GB/T 7357-1998 System design and protection of marine electrical equipment
Some standard content:
ICS 47. 020. 60 ,29. 260. 01U60
National Standard of the People's Republic of China
GB/T 7357 --- 1998
eqvIEC92-202:1994
Electrical installations in shipsSystem design Protection
Published on March 12, 1998
Implementation on October 1, 1998
Published by the State Bureau of Technical Supervision
W.GB/T7357—1998
This standard is equivalent to the 202nd article of International Electrotechnical Commission IEC92 publication "Marine electrical equipment - System design - Protection" (4th edition in March 1994) and its Revision Notice No. 1 (February 1996) to revise GB7357-87. The editing rules are in accordance with GB/T1.1-1993 Guidelines for standardization Unit 1: Rules for drafting and presentation of standards Part 1: Basic perspectives for standard writing W.bzsosocomCB/T7357—1998
IEC Foreword
1IEC (International Electrotechnical Commission) is a global standardization organization composed of all national electrotechnical committees (IEC National Committees). The purpose of the IEC is to promote international cooperation on all issues related to standardization in the electrical and electrical fields. For this purpose, as well as to carry out other activities, the IEC publishes international standards. The formulation of international standards is entrusted to technical committees; any IEC national committee with an interest in the subject may participate in the formulation of the international standard. International organizations, governmental organizations and non-governmental organizations that have relations with the IEC may also participate in the formulation of the international standard. The IEC and the International Organization for Standardization (ISO) work closely together under the conditions determined by the agreement between the two organizations.
2Formal resolutions or agreements of the International Electrotechnical Commission on technical issues, formulated by technical committees representing all national committees with a special interest in the technical issues, express the international consensus on these issues as much as possible. 3 These resolutions or agreements are published in the form of standards, technical reports or guidance documents, and are recommended for international use and accepted by the National Committees in this sense.
4 In order to "promote international unification, the IEC National Committee intends to explicitly adopt IEC international standards as their national and regional standards to the greatest extent possible. All differences between IEC standards and corresponding national or regional standards should be clearly stated in the national or regional standards.
International Standard IEC92-202 was prepared by IEC Technical Committee 18 (Electrical Equipment for Ships and Mobile and Fixed Offshore Installations). This 4th edition cancels and replaces the 1980 edition. The third edition and its amendment No. 2 (1989) constitute a technical revision. This standard should be read in conjunction with IEC 363. The text of this standard is based on the following documents: Draft International Standard (DIS) 18 (Central Office) 546 Table Quick Report 18 (Central Office) 552 Detailed information on the voting process for the approval of this standard can be found in the voting reports listed in the table above. Ww.bzsoso: com 1 Scope National Standard of the People's Republic of China Electrical installations in ships System design Electrical installations in ships-System design Protection This standard defines the main features of the system design protection of electrical installations in ships. 2 Referenced Standards GB/T 7357—1998 eqv IEC 92-202.1994
and its revision notice No. 1: 1996
replaces GR7357-87
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest version of the following standards. IEC50 (151): 1978 International Electrotechnical Vocabulary (IEV) Chapter 151: Electrical and Magnetic Devices IEC50 (441): 1984 International Electrotechnical Vocabulary (IEV) Chapter 441: Switchgear, Controlgear and Fuses 1EC92-301: 1980 Marine Electrical Equipment - Part 301: Equipment - Generators and Motors 1EC363: 1972 Short-circuit current estimation - Estimation of rated short-circuit capacity of marine circuit breakers in particular 1EC947-2: 1989 Low-voltage switchgear and controlgear - Part 2: Circuit breakers 3 Definitions
This standard adopts the following definitions.
3.1 Rated load
means the maximum value of the load specified under rated conditions. (IEC151-03-16, revised] 3.2 Overload
Overcurrent operation in a circuit that is not electrically damaged. Condition. [IEC441-11-08] 3.3 Overcurrent overeurrent
Any current exceeding the rated current value. IFC441-11-06]3.4 Short circuit
An accidental or intentional connection between two or more points in a circuit which are normally at different electrical repulsions through a relatively low resistance or impedance. EC151-03-41
35 Back-up protection
A protective device or system intended to function when a system fault is not cleared in time due to the following reasons: a) The protective device nearest the fault point fails or is unable to operate; b) The protective device other than the protective device nearest the fault point fails. 1) The definitions of these terms in the International Electrotechnical Vocabulary (IEV) are not applicable to this standard. Approved by the State Bureau of Technical Supervision on March 12, 1998 and implemented on October 1, 1998. GB/T 7357-1996 3.6 Overcurrent selectivity The operating characteristics of two or more overcurrent protective devices are coordinated so that when the magnitude of the overcurrent is within a specified range, the overcurrent protective device intended to operate within this range operates, while the other overcurrent protective devices do not operate. (IFC 441-17-15] 3.7 Total discrimination, total selectivity When two or more overcurrent protective devices are connected, the overcurrent protection device of the load will play a protective role without causing the overcurrent protection device of other overcurrent protective devices to operate. 3. Partial discrimination: partial selectivity When two or more overcurrent protective devices are connected, the overcurrent protection device closest to the fault point will play a protective role within the specified short-circuit current range and will not cause the overcurrent protection device of other overcurrent protective devices to operate. 3.9 Continuity of supply 1 Continuity of supply The condition in which continuous power supply to other normal circuits can be ensured during and after a circuit fault. Note: See circuit 3 in Figure 1. 3.10 Continuity of service: The condition in which power supply to other normal circuits can only be restored after the fault circuit is disconnected. Note: See circuit 3 in Figure 1. General requirements 4.1 Electrical equipment shall be protected against accidental overcurrent including short circuit by appropriate protective devices. The selection, matching and operating performance of various protective devices shall provide complete and coordinated automatic protection, so as to achieve the following: a) in case of a fault somewhere, the system shall ensure the continuity of power supply to normal equipment circuits through the selection of protective devices, at least ensuring the continuity of quick use (see 1); b) ensure the elimination of the impact of the fault, so as to reduce damage to the system and the risk of fire. Under these conditions, the components of the system shall be designed and manufactured to withstand the thermal stress and electromotive stress generated by the overcurrent (including short circuit) that may occur within the permitted time. 4.2 Overcurrent protective devices shall be selected according to the requirements of overload and overcurrent protection. 2
W.Supply continuity
Continuity in use
5 Circuit current
Before failure
GB/T 7357 --1998
During failure
Figure 1 Supply continuity and short-term continuity
IEC 363 gives examples of short-term calculations for AC and DC systems. 5. Short-circuit current of alternating current system
After fault
5.1.1 To estimate the expected short-circuit current, the equivalent impedance of the system should be considered from the fault point. 5.1.2 The current source should include the maximum number of generators connected at the same time and the maximum number of motors connected to the system at the same time under normal circumstances. The short-circuit current fed by them should be calculated based on the characteristics of the generators and motors. Note: If accurate data on the characteristics of the relevant parameters are used, in order to determine the maximum peak value that the torque current may reach, the short-circuit current fed by the induction motor (that is, the value of the maximum peak value of the short-circuit current of the induction motor) can be taken as R1., where 1. The system includes the sum of the rated currents of each motor used in the network under normal circumstances (table effective value),
For more accurate calculation, the following effective values can be used: 8) At the moment of short circuit (super transient value); 6.251, b) At T moment, that is, one cycle after the short circuit occurs: 2.51, e) At 21 Between groups, that is, two cycles after the short circuit occurs, 1. 0 1. W.bzsoso: com5.2 Short-circuit current of DC system
GB/T7357—1998
5.2.1 Consider using the system equivalent resistance calculated from the fault point to estimate the expected short-circuit current at a certain point in the system5.2.2 The short-circuit current source should include the maximum number of generators that may be connected at the same time and the maximum number of motors that are connected to the system at the same time under normal circumstances. The short-circuit current fed by each rotating machine should be estimated as a function of its dependent parameters. If there is a lack of accurate data, when determining the maximum value that the short-circuit current may reach, the short-circuit current fed by the motor can be taken as equal to six times the sum of the rated currents of each motor that is estimated to be used simultaneously under positive load conditions. 6 Characteristics and selection of protective devices related to short-circuit ratings 6.1 General
6.1.1 Protective devices used for short-circuit protection should be in accordance with the provisions of IEC standards for circuit breakers and fuses, but it should be taken into account that the conditions of ship electrical installations may be different from those anticipated by these standards, especially with regard to: low;
a) the short-circuit power factor of the ship's AC system, which may be lower than the power factor used as the basis for the rated short-circuit capacity of general distribution circuit breakers; b) the ultra-transient and transient components of the AC short-circuit current. Therefore, the ratio of the rated breaking capacity of the circuit breaker corresponding to the general conditions of the distribution system to the corresponding making capacity (IEC:9472) may be significantly insufficient.
In this case, the circuit breakers should be selected according to their short-circuit making capacity, even if the short-circuit breaking capacity of these breakers in general operation may exceed the short-circuit breaking capacity required for actual use. For generator circuit breakers and other circuit breakers that preferably have a predetermined short delay for short-circuit tripping, circuit breakers of utilization category B (according to IEC947-2) should be used, and they should be selected according to the rated short-time withstand current capacity of the circuit breaker. For circuit breakers without a predetermined short delay for short-circuit tripping, circuit breakers of utilization category A (according to IEC.947-2) can be used, and they should be selected according to the rated short-circuit breaking capacity of the circuit breaker. 6.1.2 Short-circuit protection shall be provided by circuit breakers or fuses. Note: In certain cases, especially for interlaced systems with voltages above 1 kV, some types of fuses have such characteristics that they should be arranged to trip an associated switch under these overcurrents. 6.1.3 If fuses or circuit breakers (but not generator circuit breakers) with at least the required rated short-circuit capacity are used as backup protection on the generator side, it is permitted to use protective devices with a short-circuit breaking capacity or short-circuit breaking force less than the total expected maximum short-circuit current at its installation point. When important equipment is not included, the same fuse or circuit breaker shall be used as backup protection for more than one circuit breaker. The short-circuit performance of the backup protection device shall be at least equal to the requirements of IEC:947-2 for a single circuit breaker of the same type of short-circuit performance as the circuit breaker being backed up and with a rated short-circuit breaking capacity calculated according to the expected maximum short-circuit current at the power supply end of the device. Circuit breakers with fuses connected to the load side may be used, provided that the circuit breaker and its backup protection fuse are designed with matching characteristics to ensure that the fuse can operate appropriately when the circuit breaker is subjected to overcurrent including the overcurrent that causes the fuse to operate, thereby preventing the generation of voltage between the poles or metal parts of the circuit breaker.
When determining the performance requirements of the above backup protection device, it is allowed to consider the impedance of each circuit element of the backup protection device. For example, when the circuit breaker with backup protection is far away from the backup protection circuit breaker or fuse, the impedance of the connecting cable can be considered. 6.2 Rated short-circuit breaking capacity
The rated short-circuit breaking capacity of each electrical device used for short-circuit protection shall not be less than the maximum expected short-circuit current to be broken at its installation point. 6.3 Rated short-circuit making capacity
Except for the exceptions specified in 6.1.3, the rated short-circuit making capacity of each mechanical switching device intended to be connected under short-circuit conditions shall be greater than the maximum peak value of the expected short-circuit current at its installation point. The circuit breaker shall be able to connect the current corresponding to its connection capacity and not disconnect within the required maximum delay time. 6.4 Coordinated selection of protective devices related to selectivity requirements 6.4.1 The power supply continuity of non-fault circuits in the case of short circuits shall be achieved using the full range of selectivity. 4
WGB/T 7357—1998
6.4.2 When non-fault circuits are required to have a continuous use certificate, the operating characteristics of both the protective device and the protected equipment shall be coordinated and verified.
6.4.3 The protective device shall be able to carry a short-circuit current not less than that at its installation point within the time required by the full range of selectivity and the partial selectivity within the specified current range without disconnecting. 7 Selection of protective devices based on overload
7.1 Mechanical switch
The tripping characteristics (overcurrent-de-suppression time) of the mechanical switch device used for overload protection shall be compatible with the overload capacity of the protected system components and any selectivity requirements.
7.2 Overload protection fuses
If the fuses have appropriate characteristics, fuses can be used for overload protection below 320A, but circuit breakers or similar devices are recommended for over 200A. For AC high voltage systems, fuses are not allowed to be used for overload protection. 8 Select protective devices according to use requirements
8. 1 General
Short-circuit protection should be provided on each non-grounded line. Except for insulated DC circuits, insulated single-phase circuits, and three-phase circuits with balanced loads, which can omit overload protection on one line, overload protection should be provided on each non-grounded line of the circuit. Short-circuit or overload protection devices should not cut off the grounding wire unless all non-grounded wires can be disconnected simultaneously by multi-pole switching devices. 8.2 Generator protection
8.2.1 General
Multi-pole circuit breakers should be used to protect the generator from short circuits and overloads. In particular, the overload protection should be adapted to the thermal capacity of the generator and should comply with the following provisions:
a) For overloads less than 10%, the use of an audible alarm signal controlled by a time delay relay set at a maximum of 1.1 times the rated current of the generator and a delay not exceeding 15 minutes may be considered: If the operating conditions require and the design of the generator allows, a delay of more than 15 minutes may also be used: b) For overloads between 10% and 50%, the circuit breaker should be delayed for a maximum of 2 minutes when it does not exceed 1.5 times the rated current of the generator; however, if the operating conditions require and the structure of the generator allows, the overload may exceed 50% and the delay may also exceed 2 minutes:
c) For overcurrents exceeding 60%, the "instantaneous" tripping should be coordinated with the selective protection of the system. In the "instantaneous" tripping device designed for short-circuit protection, a short delay may be used to meet the selectivity requirements. For large generators and all high voltage generators, protection should be provided for faults on the generator side of the circuit breaker. Notes
1 Consideration should be given to the protective devices associated with the generator, that is, they should be ensured to continue to be effective even in the case of a serious drop in the generator speed. 2 Consideration should be given to selecting protective devices as overload protection for the generator that can allow the power source to be restored immediately after the overload protective device is activated. 8.2.2 Short-circuit protection on the generator side
When generators are to be operated in parallel, consideration must be given to the fault current that needs to be cut off by the generator circuit breaker if a short circuit occurs between the generator and its circuit breaker.
Reference 1, consideration should be given to the possible danger of closing the circuit breaker that blocks the generator when the generator is not synchronized with the system to which it is connected. Generators with a capacity equal to or greater than 1500kVA should be equipped with appropriate protective devices or protection systems so that the power supply cables inside the generator or between the generator and its circuit breaker.Note 2: In special cases, for example, to protect personnel, the power supply system is too long, etc., similar protection may also be required for generators with a capacity of less than 1500kVA.
GB/T7357—1998
B.2.3 Protective devices for two-wire or three-wire DC compound generators For DC generators running in parallel, in addition to overload and short-circuit protection, the following protective devices should be installed: a) For semi-compound generators, each generator should be provided with a voltage-equalizing switch interlocked with the circuit breaker, which opens after the contacts of the relevant circuit breaker are disconnected, or a multi-pole circuit breaker that can disconnect all the circuits at the same time should be provided: b) In a three-phase system, an interlocking switch that can be operated simultaneously with the discharge switch or circuit breaker connected to the external conductor should be provided in the neutral line.
83 Protection of important electrical equipment
Where the load is composed of important equipment and non-important equipment, it should be considered to provide an automatic unloading device that can automatically cut off non-important equipment when any generator is over-attenuated to prevent the generator from continuing to slow down. This load shedding may be carried out in one or more stages, depending on the overload capacity of the generator. 8.4 Transformer protection
According to the provisions of Chapter 6, the primary windings of the transformer group shall be short-circuited by multi-pole circuit breakers or fuses. When the transformers are operated in parallel, the secondary windings shall be equipped with high-voltage switches. Note If the transformer group can be connected via the secondary windings, the secondary windings shall be short-circuited. 8.5 Line protection
8.5.1 According to the provisions of Chapter 6 and Chapter 2, each distribution line shall be short-circuited by multi-pole circuit breakers or fuses.
Note Care shall be taken to ensure that in systems where several generators are operated in parallel, the protection devices remain effective when supplied by the smallest generator. B.5.2 From the point of view of protection, multiple cables with a nominal cable area of not less than 50 mm2 connected by the cables may be used as a single cable
8. 5.3 For power supply lines of electrical equipment with independent overload protection (such as motors, see Article 6) or electrical equipment that cannot be overloaded (such as fixed wiring electric heating circuits), only short circuit protection can be installed. 8.6 Motor protection
8.6.1 Motors with a rated power exceeding 0.5kW should be equipped with overload protection. 8.6.2 For motors intended for important equipment, overload protection can be replaced by alarm devices: For motors intended for energy-saving equipment, overload protection should be replaced by alarm devices.
8. 6.3 The protective device should be designed to allow the current to pass during the acceleration period of the motor under normal use conditions. If the time-current characteristics of the motor overload protection device are not compatible with the motor running cycle, the overload protection device can be disabled during the motor speed period, provided that the short-circuit protection is still effective and the closure of the overload protection is also temporary. 8.6.4 For continuous working motors, the protective device should have the time resistance to ensure reliable thermal protection of the motor under overload conditions. 8.6.5 The maximum continuous current of the protective device should be set within the range of 105%~120% of the rated current of the protected motor. 8.6.6 For intermittent duty motors, the current setting value and delay characteristics (time function) of the protective device should be selected after considering the actual use conditions.
8.6.7 When fuses are used to protect multi-phase motor circuits, protection against single-phase operation should be considered. 8.7 Lighting circuit protection
Each lighting circuit should be protected by an appropriate device for overload and short circuit protection. B.8 Electrical connection protection
Fixed digital relays from the shore power box to the main switchboard should be protected by fuses or circuit breakers. Such protection in the switch box should not be omitted.
8.9 Battery protection
In addition to the starting battery of the engine, a protective device as close to the battery as possible should be used to protect the battery from overload and short circuit.
For important electrical equipment, emergency batteries should only be equipped with frequency protection circuit protection. W8.10 Protection of instruments, indicator lights and control circuits GB/T 7357—1998
Fuses or current limiting devices shall be used to ensure that indicating and measuring devices are protected. For other circuits, such as those of voltage regulators, where a loss of voltage may have serious consequences, fuses should not be used. If fuses are not used, measures shall be taken to prevent the risk of fire in the unprotected parts of the equipment. Fuses shall be installed as close as possible to the power plug. 8.11 Protection of stationary or solid-state equipment
To protect components and to prevent short circuits in components, stationary solid-state equipment shall be equipped with suitable current limiting fuses. Distribution circuits connecting stationary or solid-state equipment to the power supply shall be protected by circuit breakers whose tripping characteristics match those of the fuses, to ensure that components are protected from harmful overcurrents from all directions. 9 Reverse power and reverse current protection
9.1 Reverse power protection of alternators
Alternating current generators connected in parallel shall be provided with reverse active power protection with time delay. The setting value of the protective circuit breaker is usually within the range of 2% to 6% of the rated power for steam turbines and 8% to 15% of the rated power for diesel engines.
A 50% drop in the applied voltage should not invalidate the reverse power protection, although it will change the reverse power value required to open the circuit breaker. Note: The reverse current protection can be replaced by other devices that can ensure appropriate protection. 9.2 Reverse current protection of DC generators
DC generators that are connected in parallel or in parallel with batteries should be equipped with instantaneous or short-delay reverse current protection. The setting value of the protective device is usually within the range of 2% to 6% of the rated power for steam turbines and 8% to 15% of the rated power for diesel engines.
A 50% drop in the applied voltage should not invalidate the reverse current protection, although it will change the reverse current value required to open the circuit breaker. When there is a voltage-sharing line, the reverse current protection device should be connected to the pole that is not connected to the series-acting group. Notes
1 Reverse current protection should be sufficient to effectively handle reverse current from the ship's power grid (such as cargo cranes). 2 See Figure JEC92-301
10 Undervoltage protection
10.1 AC and DC generators
For generators that are connected in parallel or in parallel with shore power feeders, measures should be taken to prevent the generator circuit breaker from closing when the generator is not generating electricity and to prevent the generator from being connected to the busbar when the voltage is lost. If an undervoltage release is used for this purpose, it should act instantaneously to prevent the circuit breaker from closing, but when opening the circuit breaker, it should act with a delayed action to have a selective effect. 10.2 AC and DC motors
10.2.1 For motors with a rated power greater than 0.5 kW, one of the following two types of protection shall be provided: a) Undervoltage protection, which operates in response to a voltage drop or loss, causing and maintaining a circuit disconnection until the motor is manually restarted b) Undervoltage release, which operates in response to a voltage drop or loss, but shall be designed so that the motor can automatically restart when the voltage is restored without excessive starting current + provided that the starter (which may be controlled by, for example, a thermostatic device, pneumatic device or hydraulic device) still ensures the necessary connections for restarting, and if necessary to avoid excessive voltage drops or current surges, all motors should not be restarted at the same time. 10.2.2 The protective device shall allow the motor to run when the voltage is higher than 8% of the rated voltage: and when the voltage is lower than about 20% of the rated voltage under certain conditions, the protective device must operate, with a delay if necessary. Note that high-voltage positive protection is not necessarily required for energy-saving motors and other motors that must be used continuously. W11 Overvoltage protection
GB/T 7357-1998
11.1 Transformer
Appropriate precautions should be taken to prevent the low voltage system supplied by the transformer from being affected by the leakage of the transformer high voltage system. Grounding of the low voltage system can be regarded as an appropriate precaution.
11.2 AC motor
Appropriate precautions should be taken in the high voltage AC system to limit and (or) prevent overvoltage caused by switching conversion, etc.An automatic disconnection device should be provided to automatically disconnect non-essential equipment when any generator is overloaded to prevent the generator from continuing to slow down. This disconnection may be carried out in one or more stages, depending on the overload capacity of the generator. 8.4 Transformer protection
The primary windings of the transformer group shall be short-circuited by multi-pole circuit breakers or fuses in accordance with the provisions of Chapter 6. When the transformers are operated in parallel, the secondary windings shall be equipped with high-voltage switches. Note If the transformer group can be connected via the secondary windings, the secondary windings shall be short-circuited. 8.5 Line protection
8.5.1 Each distribution line shall be short-circuited and protected by multi-pole circuit breakers or fuses in accordance with the provisions of Chapter 6 and Chapter 7.
Note Care should be taken to ensure that in a system where several generators are operated in parallel, the protection device remains effective when supplied by the smallest generator. B.5.2 From the protection point of view, multiple cables with a nominal cable area of not less than 50 mm2 connected by cables can be used as a single cable.
8.5.3 For power supply equipment with independent overload protection (such as motors, see Article 6) or power supply equipment that cannot be overloaded (such as fixed wiring electric heating circuits), only short circuit protection can be provided. 8.6 Motor protection
8.6.1 Motors with a rated power exceeding 0.5 kW should be equipped with overload protection. 8.6.2 For motors intended for important equipment, overload protection can be replaced by alarm devices; for motors intended for power equipment, overload protection should be replaced by alarm devices.
8. 6.3 The protective device should be designed to allow the current to pass during the acceleration period of the motor under normal use conditions. If the time-current characteristics of the motor overload protection device are not compatible with the motor running cycle, the overload protection device can be disabled during the motor speed period, provided that the short-circuit protection is still effective and the closure of the overload protection is also temporary. 8.6.4 For continuous working motors, the protective device should have the time resistance to ensure reliable thermal protection of the motor under overload conditions. 8.6.5 The maximum continuous current of the protective device should be set within the range of 105%~120% of the rated current of the protected motor. 8.6.6 For intermittent duty motors, the current setting value and delay characteristics (time function) of the protective device should be selected after considering the actual use conditions.
8.6.7 When fuses are used to protect multi-phase motor circuits, protection against single-phase operation should be considered. 8.7 Lighting circuit protection
Each lighting circuit should be protected by an appropriate device for overload and short circuit protection. B.8 Electrical connection protection
Fixed digital relays from the shore power box to the main switchboard should be protected by fuses or circuit breakers. Such protection in the switch box should not be omitted.
8.9 Battery protection
In addition to the starting battery of the engine, a protective device as close to the battery as possible should be used to protect the battery from overload and short circuit.
For important electrical equipment, emergency batteries should only be equipped with frequency protection circuit protection. W8.10 Protection of instruments, indicator lights and control circuits GB/T 7357—1998
Fuses or current limiting devices shall be used to ensure that indicating and measuring devices are protected. For other circuits, such as those of voltage regulators, where a loss of voltage may have serious consequences, fuses should not be used. If fuses are not used, measures shall be taken to prevent the risk of fire in the unprotected parts of the equipment. Fuses shall be installed as close as possible to the power plug. 8.11 Protection of stationary or solid-state equipment
To protect components and to prevent short circuits in components, stationary solid-state equipment shall be equipped with suitable current limiting fuses. Distribution circuits connecting stationary or solid-state equipment to the power supply shall be protected by circuit breakers whose tripping characteristics match those of the fuses, to ensure that components are protected from harmful overcurrents from all directions. 9 Reverse power and reverse current protection
9.1 Reverse power protection of alternators
Alternating current generators connected in parallel shall be provided with reverse active power protection with time delay. The setting value of the protective circuit breaker is usually within the range of 2% to 6% of the rated power for steam turbines and 8% to 15% of the rated power for diesel engines.
A 50% drop in the applied voltage should not invalidate the reverse power protection, although it will change the reverse power value required to open the circuit breaker. Note: The reverse current protection can be replaced by other devices that can ensure appropriate protection. 9.2 Reverse current protection of DC generators
DC generators that are connected in parallel or in parallel with batteries should be equipped with instantaneous or short-delay reverse current protection. The setting value of the protective device is usually within the range of 2% to 6% of the rated power for steam turbines and 8% to 15% of the rated power for diesel engines.
A 50% drop in the applied voltage should not invalidate the reverse current protection, although it will change the reverse current value required to open the circuit breaker. When there is a voltage-sharing line, the reverse current protection device should be connected to the pole that is not connected to the series-acting group. Notes
1 Reverse current protection should be sufficient to effectively handle reverse current from the ship's power grid (such as cargo cranes). 2 See Figure JEC92-301
10 Undervoltage protection
10.1 AC and DC generators
For generators that are connected in parallel or in parallel with shore power feeders, measures should be taken to prevent the generator circuit breaker from closing when the generator is not generating electricity and to prevent the generator from being connected to the busbar when the voltage is lost. If an undervoltage release is used for this purpose, it should act instantaneously to prevent the circuit breaker from closing, but when opening the circuit breaker, it should act with a delayed action to have a selective effect. 10.2 AC and DC motors
10.2.1 For motors with a rated power greater than 0.5 kW, one of the following two types of protection shall be provided: a) Undervoltage protection, which operates in response to a voltage drop or loss, causing and maintaining a circuit disconnection until the motor is manually restarted b) Undervoltage release, which operates in response to a voltage drop or loss, but shall be designed so that the motor can automatically restart when the voltage is restored without excessive starting current + provided that the starter (which may be controlled by, for example, a thermostatic device, pneumatic device or hydraulic device) still ensures the necessary connections for restarting, and if necessary to avoid excessive voltage drops or current surges, all motors should not be restarted at the same time. 10.2.2 The protective device shall allow the motor to run when the voltage is higher than 8% of the rated voltage: and when the voltage is lower than about 20% of the rated voltage under certain conditions, the protective device must operate, with a delay if necessary. Note that high-voltage positive protection is not necessarily required for energy-saving motors and other motors that must be used continuously. W11 Overvoltage protection
GB/T 7357-1998
11.1 Transformer
Appropriate precautions should be taken to prevent the low voltage system supplied by the transformer from being affected by the leakage of the transformer high voltage system. Grounding of the low voltage system can be regarded as an appropriate precaution.
11.2 AC motor
Appropriate precautions should be taken in the high voltage AC system to limit and (or) prevent overvoltage caused by switching conversion, etc.An automatic disconnection device should be provided to automatically disconnect non-essential equipment when any generator is overloaded to prevent the generator from continuing to slow down. This disconnection may be carried out in one or more stages, depending on the overload capacity of the generator. 8.4 Transformer protection
The primary windings of the transformer group shall be short-circuited by multi-pole circuit breakers or fuses in accordance with the provisions of Chapter 6. When the transformers are operated in parallel, the secondary windings shall be equipped with high-voltage switches. Note If the transformer group can be connected via the secondary windings, the secondary windings shall be short-circuited. 8.5 Line protection
8.5.1 Each distribution line shall be short-circuited and protected by multi-pole circuit breakers or fuses in accordance with the provisions of Chapter 6 and Chapter 7.
Note Care should be taken to ensure that in a system where several generators are operated in parallel, the protection device remains effective when supplied by the smallest generator. B.5.2 From the protection point of view, multiple cables with a nominal cable area of not less than 50 mm2 connected by cables can be used as a single cable.
8.5.3 For power supply equipment with independent overload protection (such as motors, see Article 6) or power supply equipment that cannot be overloaded (such as fixed wiring electric heating circuits), only short circuit protection can be provided. 8.6 Motor protection
8.6.1 Motors with a rated power exceeding 0.5 kW should be equipped with overload protection. 8.6.2 For motors intended for important equipment, overload protection can be replaced by alarm devices; for motors intended for power equipment, overload protection should be replaced by alarm devices.
8. 6.3 The protective device should be designed to allow the current to pass during the acceleration period of the motor under normal use conditions. If the time-current characteristics of the motor overload protection device are not compatible with the motor running cycle, the overload protection device can be disabled during the motor speed period, provided that the short-circuit protection is still effective and the closure of the overload protection is also temporary. 8.6.4 For continuous working motors, the protective device should have the time resistance to ensure reliable thermal protection of the motor under overload conditions. 8.6.5 The maximum continuous current of the protective device should be set within the range of 105%~120% of the rated current of the protected motor. 8.6.6 For intermittent duty motors, the current setting value and delay characteristics (time function) of the protective device should be selected after considering the actual use conditions.
8.6.7 When fuses are used to protect multi-phase motor circuits, protection against single-phase operation should be considered. 8.7 Lighting circuit protection
Each lighting circuit should be protected by an appropriate device for overload and short circuit protection. B.8 Electrical connection protection
Fixed digital relays from the shore power box to the main switchboard should be protected by fuses or circuit breakers. Such protection in the switch box should not be omitted.
8.9 Battery protection
In addition to the starting battery of the engine, a protective device as close to the battery as possible should be used to protect the battery from overload and short circuit.
For important electrical equipment, emergency batteries should only be equipped with frequency protection circuit protection. W8.10 Protection of instruments, indicator lights and control circuits GB/T 7357—1998
Fuses or current limiting devices shall be used to ensure that indicating and measuring devices are protected. For other circuits, such as those of voltage regulators, where a loss of voltage may have serious consequences, fuses should not be used. If fuses are not used, measures shall be taken to prevent the risk of fire in the unprotected parts of the equipment. Fuses shall be installed as close as possible to the power plug. 8.11 Protection of stationary or solid-state equipment
To protect components and to prevent short circuits in components, stationary solid-state equipment shall be equipped with suitable current limiting fuses. Distribution circuits connecting stationary or solid-state equipment to the power supply shall be protected by circuit breakers whose tripping characteristics match those of the fuses, to ensure that components are protected from harmful overcurrents from all directions. 9 Reverse power and reverse current protection
9.1 Reverse power protection of alternators
Alternating current generators connected in parallel shall be provided with reverse active power protection with time delay. The setting value of the protective circuit breaker is usually within the range of 2% to 6% of the rated power for steam turbines and 8% to 15% of the rated power for diesel engines.
A 50% drop in the applied voltage should not invalidate the reverse power protection, although it will change the reverse power value required to open the circuit breaker. Note: The reverse current protection can be replaced by other devices that can ensure appropriate protection. 9.2 Reverse current protection of DC generators
DC generators that are connected in parallel or in parallel with batteries should be equipped with instantaneous or short-delay reverse current protection. The setting value of the protective device is usually within the range of 2% to 6% of the rated power for steam turbines and 8% to 15% of the rated power for diesel engines.
A 50% drop in the applied voltage should not invalidate the reverse current protection, although it will change the reverse current value required to open the circuit breaker. When there is a voltage-sharing line, the reverse current protection device should be connected to the pole that is not connected to the series-acting group. Notes
1 Reverse current protection should be sufficient to effectively handle reverse current from the ship's power grid (such as cargo cranes). 2 See Figure JEC92-301
10 Undervoltage protection
10.1 AC and DC generators
For generators that are connected in parallel or in parallel with shore power feeders, measures should be taken to prevent the generator circuit breaker from closing when the generator is not generating electricity and to prevent the generator from being connected to the busbar when the voltage is lost. If an undervoltage release is used for this purpose, it should act instantaneously to prevent the circuit breaker from closing, but when opening the circuit breaker, it should act with a delayed action to have a selective effect. 10.2 AC and DC motors
10.2.1 For motors with a rated power greater than 0.5 kW, one of the following two types of protection shall be provided: a) Undervoltage protection, which operates in response to a voltage drop or loss, causing and maintaining a circuit disconnection until the motor is manually restarted b) Undervoltage release, which operates in response to a voltage drop or loss, but shall be designed so that the motor can automatically restart when the voltage is restored without excessive starting current + provided that the starter (which may be controlled by, for example, a thermostatic device, pneumatic device or hydraulic device) still ensures the necessary connections for restarting, and if necessary to avoid excessive voltage drops or current surges, all motors should not be restarted at the same time. 10.2.2 The protective device shall allow the motor to run when the voltage is higher than 8% of the rated voltage: and when the voltage is lower than about 20% of the rated voltage under certain conditions, the protective device must operate, with a delay if necessary. Note that high-voltage positive protection is not necessarily required for energy-saving motors and other motors that must be used continuously. W11 Overvoltage protection
GB/T 7357-1998
11.1 Transformer
Appropriate precautions should be taken to prevent the low voltage system supplied by the transformer from being affected by the leakage of the transformer high voltage system. Grounding of the low voltage system can be regarded as an appropriate precaution.
11.2 AC motor
Appropriate precautions should be taken in the high voltage AC system to limit and (or) prevent overvoltage caused by switching conversion, etc.4 For continuous duty motors, the protective device should have the time capability to ensure reliable thermal protection of the motor under overload conditions. 8.6.5 The maximum continuous current of the protective device should be set within the range of 105% to 120% of the rated current of the protected motor. 8.6.6 For intermittent duty motors, the current setting value and delay characteristics (time function) of the protective device should be selected after considering the actual use conditions.
8.6.7 When fuses are used to protect multi-phase motor circuits, protection against single-phase operation should be considered. 8.7 Lighting circuit protection www.bzxz.net
Each lighting circuit should be protected by an appropriate device for overload and short circuit protection. B.8 Electrical connection protection
The fixed number of relays from the shore power box to the main switchboard should be protected by fuses or circuit breakers. This protection in the switch box should not be omitted.
8.9 Battery protection
Except for the starting battery of the engine, the battery should be protected against overload and short circuit by protective devices installed as close to the battery as possible
For the battery supplying important electrical equipment, only overload and short circuit protection should be provided. 8.10 Protection of instruments, indicator lights and control circuits GB/T 7357—1998
Fuses or current limiting devices should be used to ensure the protection of indicating devices and measuring devices. For other circuits, such as the circuit of the voltage regulator, where the loss of voltage may have serious consequences, it is not appropriate to use fuses. If fuses are not used, measures should be taken to prevent the fire hazard of the unprotected part of the equipment. The fuse should be installed as close to the power plug as possible. 8.11 Protection of stationary or solid-state equipment
In order to protect the components and to prevent the influence of short circuits in the components, stationary solid-state equipment should be equipped with suitable current limiting fuses. Distribution circuits connecting stationary or solid-state equipment to the supply shall be protected by circuit breakers whose tripping characteristics match the breaking characteristics of fuses to ensure that the components are protected from harmful overcurrents from all directions. 9 Reverse power and reverse current protection
9.1 Reverse power protection for AC generators
AC generators connected in parallel shall be provided with reverse active power protection with time delay. The setting value of the protection switch shall normally be in the range of 2% to 6% of the rated power for steam turbines and in the range of 8% to 15% of the rated power for diesel engines.
A drop of 50% in the applied voltage shall not render the reverse power protection ineffective, although it will change the reverse power value required to open the circuit breaker. NOTE: Reverse current protection may be replaced by other devices that ensure adequate protection. 9.2 Reverse current protection for DC generators
DC generators connected in parallel or in parallel with batteries shall be provided with instantaneous or short-delay reverse current protection. The setting value of the protective device is usually within the range of 2% to 3% of the rated power for steam turbines and 8% to 15% of the rated power for diesel engines.
A 50% drop in the applied voltage should not cause the reverse current protection to fail, although it will change the reverse current value required to open the circuit breaker. When there is a voltage-equalizing line, the reverse current protection device should be connected to the pole that is not connected to the series-acting group. Notes
1 The reverse current protection should be sufficient to effectively handle the reverse current from the ship's power grid (such as cargo cranes). 2 See Figure JEC92-301
10 Undervoltage protection
10.1 AC and DC generators
For generators that are connected in parallel or in parallel with the shore power feeder, measures should be taken to prevent the generator breaker from closing when the generator is not generating electricity and to prevent the generator from being connected to the busbar when the voltage is lost. If an undervoltage release is used for this purpose, it shall operate instantaneously to prevent the circuit breaker from closing, but shall operate with a delayed action in order to have a selective effect on opening the circuit breaker. 10.2 AC and DC motors
10.2.1 Motors with a rated power greater than 0.5 kW shall be provided with one of the following two types of protection: a) Undervoltage protection, which operates in response to a voltage drop or loss, causing and maintaining circuit disconnection until the motor is restarted manually b) Undervoltage release, which operates in response to a voltage drop or loss, but shall be designed so that the motor can be restarted automatically when the voltage is restored without excessive starting current, provided that the starter (which may be controlled, for example, by a thermostatic device, pneumatic or hydraulic device) still ensures the connections necessary for restarting and that all motors are not restarted simultaneously if this is necessary to avoid excessive voltage drops or current surges. 10.2.2 When the voltage is higher than 8% of the rated voltage, the protective device shall allow the motor to overrun; when the voltage is lower than about 20% of the rated voltage under vehicle requirements, the protective device must operate, with a delay if necessary. Note that high-voltage positive protection is not necessarily required for energy-saving motors and other motors that must be used continuously. W11 Overvoltage protection
GB/T 7357-1998
11.1 Transformer
Appropriate precautions should be taken to prevent the low-voltage system powered by the transformer from being affected by the leakage of the transformer high-voltage system. Grounding of the low-voltage system can be regarded as an appropriate precaution.
11.2 AC motor
Appropriate precautions should be taken in high-voltage AC systems to limit and (or) prevent overvoltages caused by switching, etc.4 For continuous duty motors, the protective device should have the time capability to ensure reliable thermal protection of the motor under overload conditions. 8.6.5 The maximum continuous current of the protective device should be set within the range of 105% to 120% of the rated current of the protected motor. 8.6.6 For intermittent duty motors, the current setting value and delay characteristics (time function) of the protective device should be selected after considering the actual use conditions.
8.6.7 When fuses are used to protect multi-phase motor circuits, protection against single-phase operation should be considered. 8.7 Lighting circuit protection
Each lighting circuit should be protected by an appropriate device for overload and short circuit protection. B.8 Electrical connection protection
The fixed number of relays from the shore power box to the main switchboard should be protected by fuses or circuit breakers. This protection in the switch box should not be omitted.
8.9 Battery protection
Except for the starting battery of the engine, the battery should be protected against overload and short circuit by protective devices installed as close to the battery as possible
For the battery supplying important electrical equipment, only overload and short circuit protection should be provided. 8.10 Protection of instruments, indicator lights and control circuits GB/T 7357—1998
Fuses or current limiting devices should be used to ensure the protection of indicating devices and measuring devices. For other circuits, such as the circuit of the voltage regulator, where the loss of voltage may have serious consequences, it is not appropriate to use fuses. If fuses are not used, measures should be taken to prevent the fire hazard of the unprotected part of the equipment. The fuse should be installed as close to the power plug as possible. 8.11 Protection of stationary or solid-state equipment
In order to protect the components and to prevent the influence of short circuits in the components, stationary solid-state equipment should be equipped with suitable current limiting fuses. Distribution circuits connecting stationary or solid-state equipment to the supply shall be protected by circuit breakers whose tripping characteristics match the breaking characteristics of fuses to ensure that the components are protected from harmful overcurrents from all directions. 9 Reverse power and reverse current protection
9.1 Reverse power protection for AC generators
AC generators connected in parallel shall be provided with reverse active power protection with time delay. The setting value of the protection switch shall normally be in the range of 2% to 6% of the rated power for steam turbines and in the range of 8% to 15% of the rated power for diesel engines.
A drop of 50% in the applied voltage shall not render the reverse power protection ineffective, although it will change the reverse power value required to open the circuit breaker. NOTE: Reverse current protection may be replaced by other devices that ensure adequate protection. 9.2 Reverse current protection for DC generators
DC generators connected in parallel or in parallel with batteries shall be provided with instantaneous or short-delay reverse current protection. The setting value of the protective device is usually within the range of 2% to 3% of the rated power for steam turbines and 8% to 15% of the rated power for diesel engines.
A 50% drop in the applied voltage should not cause the reverse current protection to fail, although it will change the reverse current value required to open the circuit breaker. When there is a voltage-equalizing line, the reverse current protection device should be connected to the pole that is not connected to the series-acting group. Notes
1 The reverse current protection should be sufficient to effectively handle the reverse current from the ship's power grid (such as cargo cranes). 2 See Figure JEC92-301
10 Undervoltage protection
10.1 AC and DC generators
For generators that are connected in parallel or in parallel with the shore power feeder, measures should be taken to prevent the generator breaker from closing when the generator is not generating electricity and to prevent the generator from being connected to the busbar when the voltage is lost. If an undervoltage release is used for this purpose, it shall operate instantaneously to prevent the circuit breaker from closing, but shall operate with a delayed action in order to have a selective effect on opening the circuit breaker. 10.2 AC and DC motors
10.2.1 Motors with a rated power greater than 0.5 kW shall be provided with one of the following two types of protection: a) Undervoltage protection, which operates in response to a voltage drop or loss, causing and maintaining circuit disconnection until the motor is restarted manually b) Undervoltage release, which operates in response to a voltage drop or loss, but shall be designed so that the motor can be restarted automatically when the voltage is restored without excessive starting current, provided that the starter (which may be controlled, for example, by a thermostatic device, pneumatic or hydraulic device) still ensures the connections necessary for restarting and that all motors are not restarted simultaneously if this is necessary to avoid excessive voltage drops or current surges. 10.2.2 When the voltage is higher than 8% of the rated voltage, the protective device shall allow the motor to overrun; when the voltage is lower than about 20% of the rated voltage under vehicle requirements, the protective device must operate, with a delay if necessary. Note that high-voltage positive protection is not necessarily required for energy-saving motors and other motors that must be used continuously. W11 Overvoltage protection
GB/T 7357-1998
11.1 Transformer
Appropriate precautions should be taken to prevent the low-voltage system powered by the transformer from being affected by the leakage of the transformer high-voltage system. Grounding of the low-voltage system can be regarded as an appropriate precaution.
11.2 AC motor
Appropriate precautions should be taken in high-voltage AC systems to limit and (or) prevent overvoltages caused by switching, etc.Motors over 5 kW shall be provided with one of the following two types of protection: a) undervoltage protection, which operates in response to a voltage drop or loss, causing and maintaining a circuit disconnection until the motor is manually restarted; b) undervoltage release, which operates in response to a voltage drop or loss, but shall be designed so that the motor can automatically restart when the voltage is restored without excessive starting current, provided that the starter (which may be controlled by, for example, a thermostatic device, pneumatic device or hydraulic device) still ensures the necessary connections for restarting, and if necessary to avoid excessive voltage drops or current surges, all motors should not be restarted at the same time. 10.2.2 The protective device shall allow the motor to run when the voltage is higher than 8% of the rated voltage: and when the voltage is lower than about 20% of the rated voltage under certain vehicle conditions, the protective device must operate, with a delay if necessary. Note that high-voltage positive protection is not necessarily required for energy-saving motors and other motors that must be used continuously. W11 Overvoltage protection
GB/T 7357-1998
11.1 Transformer
Appropriate precautions should be taken to prevent the low voltage system supplied by the transformer from being affected by the leakage of the transformer high voltage system. Grounding of the low voltage system can be regarded as an appropriate precaution.
11.2 AC motor
Appropriate precautions should be taken in the high voltage AC system to limit and (or) prevent overvoltage caused by switching conversion, etc.Motors over 5 kW shall be provided with one of the following two types of protection: a) undervoltage protection, which operates in response to a voltage drop or loss, causing and maintaining a circuit disconnection until the motor is manually restarted; b) undervoltage release, which operates in response to a voltage drop or loss, but shall be designed so that the motor can automatically restart when the voltage is restored without excessive starting current, provided that the starter (which may be controlled by, for example, a thermostatic device, pneumatic device or hydraulic device) still ensures the necessary connections for restarting, and if necessary to avoid excessive voltage drops or current surges, all motors should not be restarted at the same time. 10.2.2 The protective device shall allow the motor to run when the voltage is higher than 8% of the rated voltage: and when the voltage is lower than about 20% of the rated voltage under certain vehicle conditions, the protective device must operate, with a delay if necessary. Note that high-voltage positive protection is not necessarily required for energy-saving motors and other motors that must be used continuously. W11 Overvoltage protection
GB/T 7357-1998
11.1 Transformer
Appropriate precautions should be taken to prevent the low voltage system supplied by the transformer from being affected by the leakage of the transformer high voltage system. Grounding of the low voltage system can be regarded as an appropriate precaution.
11.2 AC motor
Appropriate precautions should be taken in the high voltage AC system to limit and (or) prevent overvoltage caused by switching conversion, etc.
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