Some standard content:
National Standard of the People's Republic of China
Electrical relays
Part 20: Prolectlon (protective) systems This standard adopts the international standard IE255-20 (1984) & Electrical relays 1 Subject content and scope of application
This standard specifies the performance requirements of the entire protection system and its components, GB/T 14598. 8--1995
1EC 255-20-1084
Part 20: Factoring systems".
This standard applies to the protection devices in the protection system and the devices connected to the protection devices that affect their performance. This standard applies to the following objects:
Manufacturers of protection systems or their components;
Users of protection systems:
Manufacturers of control panels:
Electrical equipment installers;
Consultants and engineers.
Different IEC standards specify the technical requirements for the components of the protection system. The relevant parts of this standard refer to these standards. Appendix A shows the power block diagram of a certain protection system. The figure also shows the relevant EC technical committees that have formulated the technical specifications for the components of the protection system.
It is recommended that the decisions made by users should be consistent with the provisions of the relevant technical committees, which are responsible for the entire protection system.
2 Terminology
The technical description refers to Chapter 448 of the International Electrical Dictionary of IEC 50 (148): Power System Protection. In addition, this standard also refers to the following scientific terms and definitions.
2.1 Protection system pruterliun systemlemn—prolective systemiem A complete set of equipment consisting of protection devices and other devices to complete the specified functions according to the protection principle. 2.2 Accelerated distance protection system accelerated distance protection systemlem·A distance protection system supplemented by communication, in which when a signal is received, it is allowed to reduce the total action time for any measurement area.
2.3 Blocking scheme bluring scheme
A protection system that sends a signal to prohibit tripping at other ends when a fault outside the protection zone is detected. Instructions for use:
The door adopts the definition of IEC50 (448).
! The sequential quick-cut distance protection does not use communication. Approved by the State Administration of Technical Supervision on July 24, 1995 and implemented on August 1, 1996
GB/T 14598.8—1995
2.4 Current transformers in idle shunts Current transformers in idle shunts are connected to the protection system but do not carry the primary current. 2.5 Circuit-breaker failure protection system Circuit-breaker fail prolection system When the selected circuit breaker fails to trip and cannot cut off the fault current, the specified circuit breaker is tripped to cut off the system fault. A protection system
2.6 De-blocking scheme system A scheme that transmits continuous blocking signals from each end of the protection zone and releases the blocking scheme when a fault current input is detected at either end. 2.7 Direction comparison protection system A protection system that uses the voltage or current obtained locally as a reference to compare the direction of the current at each end of the protected area. 2.8 Protection system associated with signaling system A protection system that requires communication between the ends of the protected circuit. 2.9 Internal fault current test A test that simulates the fault current in the protected area. 2.10 Intertripping system Sends a signal to cause the remote circuit breaker to trip directly without requiring the remote protection device to operate. 2.11 Longitudinal differential pilot wire system A differential protection system in which the differential current is equal to the algebraic sum of the currents flowing into the protected area. 2.12 Parameter of a protection system A quantity that is not affected by changes in other quantities and can be given different values under different circumstances. For example, the characteristics of the device, the power consumption of the lead wire, etc.
2.13 Permissive overreach distance protection system In fault detection, when the end protection extension detects that the fault occurs in the protection positive direction, it sends a signal to the other ends. When the other ends receive the signal, they determine that the fault occurs in the relay contact of the protection positive direction of the end, and trip the circuit breaker at that end.
2.14 Permissive underreach distance protection system A protection system that sends a signal to the other ends when a fault is detected in the first section of the distance protection at the end of the protection zone. When the other ends receive the signal, the circuit breaker at that end is tripped through the protection contact that detects the fault without directionality. 2.15 Phase comparison carrier system A protection system that compares the phase angle between the currents at each end of the protected zone. 2.16 Primary test
A test performed by applying current to the primary winding of the instrument transformer that is part of the protection system. 2.17 Stability limit of protection The limit value of any excitation quantity or influencing quantity that makes the protection inoperative in all cases except the specified operation. 2.18 Residual connection connectian The connection method of the secondary winding of the instrument transformer in order to obtain the algebraic sum of all line currents or phase voltages in a multiphase system. 2.19 Sensitivity sensitivity
The minimum value of the excitation required to just cause the relay to operate under specified conditions. 2.20 Through-current through-currcnt The current flowing through the protected area to a certain point outside the area. 2.21 Through-fault test A test using a unit protection circuit, in which the fault current passes through the protected area and flows to the fault outside the area. 3 Instrument transformers for protection systems
3.1 General requirements
GB/T 14598.81995
Manufacture of a given type of protection device (such as a given type of distance protection device). In order to ensure the predetermined performance of the protection device, the necessary technical requirements for instrument transformers should be specified in accordance with the corresponding IEC standards or corresponding national standards. If it is necessary to put forward special requirements, the manufacturer shall determine their contents (such as transient process, saturation degree, etc.) according to Appendix B or relevant standards. All these requirements apply to the main instrument transformer and the auxiliary instrument transformer. 3.2 Current transformer
Current transformers shall comply with the requirements of IFC185 "Current Transformer" or the requirements of the relevant national standards (see Appendix H). Special requirements for transient performance shall be agreed upon by the manufacturer and the user. 3.3 Voltage transformers and capacitive voltage transformers. Voltage transformers and capacitive voltage transformers shall comply with the requirements of IFC186 "Voltage Transformers" or the requirements of the relevant national standards (see Appendix H).
4 AC input excitation circuit
4.1 General requirements
The manufacturer of the protection device shall provide the necessary information and technical specifications for the formation of the AC input excitation circuit. IEC255-5 "Electrical relays Part 5: Insulation test for electrical relays" (see Appendix II) stipulates that the circuit directly connected to the instrument transformer should be able to withstand a dielectric strength test of at least 2kV voltage, so between the instrument transformer, wire and device.Insulation coordination should be performed.
The protection system withstands impulse voltage according to the 0~15kV level specified in IEC255-5. Measures should be taken to avoid surge overvoltages in the AC conductor that exceed the withstand capacity of the protection device. However, any equipment that may cause voltage (or current) amplitude and waveform distortion should be avoided. For grounding and shielding, see Chapter 11 and Appendix E. 4.2 Voltage circuit
For protection devices with voltage input, the manufacturer should explain whether a certain reason, such as the disappearance of secondary voltage under load current, may cause the protection device to malfunction and whether the device will issue an alarm and (or) perform a lockout. 4.3 Current circuit
In the plug-in relay or test connector in the secondary current circuit of the current transformer, the current circuit should not be open during all insertion and extraction processes. When: the protection system includes some special components (plug-in relays, test devices, etc.) for shorting the primary circuit of the current transformer, the relevant IC standards should specify the current withstand values of these devices. The maximum peak voltage at the maximum fault current in any current circuit shall be consistent with the insulation of the AC conductor and the secondary winding of the current transformer (for example, in a high impedance differential wiring scheme).
In order to balance or stabilize special types of protection systems, the manufacturer of the protection device shall specify special requirements for the secondary load of the current transformer (for example, differential current system, zero sequence current system, etc.). 5 Auxiliary power supply
5.1 General requirements
The manufacturer of the protection device shall provide the necessary information and technical requirements to ensure that the protection device has a satisfactory auxiliary power supply, see Appendix C. Measures should be taken to avoid the auxiliary power supply from generating surge overvoltages that exceed the withstand capacity of the protection device, see Appendix E. Instructions for use:
1_ This standard adds Appendix H (references) to list the national standards corresponding to the IEC standard. ..com5.2 DC auxiliary power supply
5.2.1 Preferred standard ratings1
GB/T 14598.8—1995
According to IEC: 255-3 Electrical relays Part 3: Other time-limited single-input excitation and measurement relays" and 255.6 "Part 6: Measuring relays and protection devices\, the preferred standard ratings of the DC auxiliary power supply voltage are; 24V, 48V, 60V110V, 125V, 220V and 250V.
The preferred limit values of the auxiliary excitation operating range are: 80% and 110% of the rated value. In the case of battery excitation, when the limit values of the operating range are different from the above preferred values, the manufacturer of the protection device shall specify the limit values of its operating range and the corresponding rated values. For grounding issues, see Chapter 11 and Record D. 5.2.2 Interruption of DC auxiliary voltage
The requirements for interruption of DC auxiliary voltage are specified in IEC255-11$ Electrical relays Part 11: Interruption and separation of DC auxiliary excitation (induced voltage) for measuring relays. The manufacturer of the protection device shall indicate whether the device can monitor the loss of DC auxiliary power supply. The protection device should not be damaged or malfunction when the DC auxiliary power supply is used or interrupted, or when reverse polarity is excited. 5.2.3 DC/DC converter
The output characteristics of DC/DC converters (for example, for exciting several protection devices working in parallel) are not included in this standard. Regarding the electrical isolation between input and output circuits, see Clause 11.3. The input current should be limited when the output terminals are shorted or when the input voltage is suddenly applied. 6 Tripping and closing circuits
See Appendix F,
6.1 General requirements
The tripping circuit has a variety of configurations. If automatic fast reclosing or slow reclosing is used and the reclosing is initiated by the protection device, the closing circuit is part of the protection system. 6.2 Tripping and closing contacts
The tripping and closing contacts of the protection system should be able to close the tripping and closing currents of the circuit breaker. And can pass this current within a specified time. If properly arranged (current holding relay, auxiliary contacts, etc.), these contacts do not need to disconnect the tripping and closing currents. See IEC255-0-20 Electrical relays, electrical relay contact performance". 6.3 Internal circuit of the circuit breaker
The characteristics of the auxiliary contacts, closing and tripping coils of the circuit breaker, the locking characteristics (if any) and the anti-tripping characteristics shall comply with the provisions of the following IEC standards:
56-1 High-voltage AC circuit breakers, Part 1: General and terminology. 56-2 Part 2: Ratings.
56-3 Part 3: Equipment and manufacture.
56-4 Part 4, Type test and routine test. 565 Part 4: Selection rules for operating circuit breakers. 56-6 Part 6, Information provided with enquiries, bids and orders and rules for transportation, installation and maintenance. Adoption instructions:
1 The original IF255-3 standard quoted in this article has been modified. IEC255-1 has been abolished. This article is now written in accordance with the revised TEC255-3.IFC255-6.
..com7 Logic circuits
7.1--General requirements
GB/T14598.8-1995
A power station switchgear may need to be equipped with measuring and tripping circuits of the switching protection system. These switching circuits are called AC and DC logic circuits in this standard. It does not include the logic circuits inside the protection device, such as any switching inside the distance protection. If alternate switching is required, such as switching to a bypass circuit breaker or another set of busbars, the protection system should have a logic circuit that adapts to this situation in the power station. In order to adapt the protection system to the high-voltage distribution equipment in the station, it is necessary to have a logic circuit (DC logic) between the protection device and the tripping and switching circuits, and sometimes a logic circuit (AC logic) is also required in the input excitation circuit. The switching of the logic circuit can be done manually or automatically. In the case of automatic switching, the logic circuit is controlled by the auxiliary contacts of the disconnector and the circuit breaker.
7.2 Logic in AC circuits
Switching can be performed in current transformer and voltage transformer circuits (such as busbar protection). See Section 4.3. 7.3 Logic in DC circuits
The DC logic switching circuit should be able to close, carry and disconnect the maximum current during normal operation, and withstand the specified short-circuit current within the specified time.
8 Communication requirements for protection systems
8.1 General requirements
For a variety of reasons, the protection system may need to have a communication channel to contact a remote substation. Sometimes analog quantities are transmitted to the other end of the power line and compared with the electrical quantities at that end there (such as pilot line schemes). The communication link of the protection system can be a pilot line link, a power line carrier link or a radio link door. 8.2 Remote tripping scheme
Should be adopted High reliability signals (such as coded signals) should be used to avoid false operations caused by noise (voltage). If power line carrier is used as the communication medium, (signal) transmission should be carried out on the non-fault line. The maximum allowable transmission time of the signal from the local end to the remote end should be specified. 8.3 Distance protection signal transmission scheme
8.3.1 General requirements
There are many different signal transmission schemes, the most commonly used are: acceleration scheme, locking scheme, unlocking scheme, permissive over-range scheme, permissive under-range scheme, and direction comparison scheme. 8.3.2 Technical requirements
The technical requirements listed in this clause are as follows: Technical requirements apply to all schemes specified in Article 8.3.1: The protection system cannot malfunction due to noise (voltage) or signal attenuation caused by circuit breaker and disconnector operation (see IEC255-22-1 "Electrical interference test for measuring relays and protection devices MHz pulse (attenuated oscillation wave) interference resistance test") 41. b. "When one of the two parallel lines sends a signal, it should not cause the protection system of the non-fault line to malfunction. When the signal is transmitted under the power line fault state, additional noise and attenuation may be introduced into the circuit. The protection system should be able to receive the signal sent by the protection. c. The user should specify the maximum allowable time for the signal to be transmitted from the local end to the remote end. (The requirements for the sending and receiving relays should be agreed upon between the manufacturer and the user). 8.4 Longitudinal differential guide wire system
Instructions for use:
1] Also includes optical cable connection.
2] The original 1EC:255-6 has been revised to relays and protection devices, and the original standard Appendix C has been formulated into a separate standard 1EC:255.22-1. GB/T 14598.8—1995
The malfunction or failure of the protection system in the event of a fault in the pilot line depends on the design of the protection system. Monitoring relays may be used to monitor the pilot line and to give an alarm in the event of a pilot line fault. When monitoring is used, the monitoring device shall be able to detect the reduction in the insulation resistance of the pilot line before it falls to a level that may cause the protection system to malfunction.
The insulation resistance and the maximum permissible loop resistance and pilot line capacitance shall be specified by the manufacturer. 8.5 Power line carrier communication
When power line carrier communication is used, the signal is not normally transmitted continuously, but the instrument is allowed to transmit a signal when a fault is detected. However, the signal transmission may be automatically interrupted for a short period of time at a set time to enable any degradation of the signal path caused by climatic conditions to be detected.
The maximum permissible channel loss, including high-frequency coupling equipment, shall be specified by the manufacturer. It will vary according to whether the coupling is phase-to-phase or phase-to-ground, and also according to which phase is used and whether there is conductor transposition and attenuation in the protection zone.
9' Signal indication
The information about the operation of the protection device shall be indicated by appropriate means. The signal indication may be displayed locally on the protection device or transmitted to a remote control center or (and) to an event recorder. The local signal indication shall have a retention function. The signal indication waiting for confirmation shall not prevent the protection device from repeated operation, even during the confirmation period.
The information of the remote signal indication usually generated by the protection device contacts is obtained during the duration of the fault, for example, the make contact is disconnected when the protection is reset. The storage of information is one of the functions of the signal indication device. 10 Insulation
10.1 Primary connection
If the protection system is directly excited by the current and (or) voltage in the main circuit or excited through a shunt without an intermediate instrument transformer, the insulation requirements are related to the rated insulation voltage of the main circuit. 10.2 Secondary connection
If the protection system is excited by instrument transformers, the circuits directly connected to the instrument transformers shall be able to withstand a dielectric strength test voltage of at least 2kV AC RMS for 60 seconds between electrically separated circuits and between these circuits and ground. When an isolation transformer is connected between the protection device and the main instrument transformer, the dielectric strength test voltage applied to the device connected to the secondary side may be reduced by negotiation between the manufacturer and the user. However, it shall not be less than 500V. 10.3 Insulation requirements for instrument transformers
The insulation requirements for instrument transformers shall comply with the provisions of IEC185 and IEC186 or the corresponding national standards. 10.4 Insulation requirements for relays
The general insulation of relays used in protection shall comply with the requirements of IEC255-5 standard. For specific types of relays, the additional requirements are already specified in the relevant parts of IF255, such as 1EC255100 & With or without electrical relays
10.5 Insulation requirements for DC auxiliary circuits (including tripping and signal indication circuits, but not including pilot line circuits). The insulation requirements for auxiliary circuits powered by dog relays shall comply with the provisions of IEC 255-5. The insulation requirements for tripping circuits are already specified in IEC 56-1~56-6.
Instructions for use:
Gate-permitted passband continuous frequency monitoring signal. ..com11 Grounding
11. 1 General requirements
GB/T 14598.8—1995
When designing the grounding system and selecting the grounding point, the possible impact of transient processes and the requirements for frequent operation of the power system should be considered. Unless grounding and (or) shielding measures have been considered, transient overvoltages that cannot be ignored will appear in the secondary circuits induced by the switching surface. 11.2 Instrument transformers
The secondary circuits of instrument transformers shall be directly grounded and only at a common point, which is connected to each individual metal system. The cross-section of the connecting wire to the protective earthing terminal shall comply with national standards. The secondary circuits of the intermediate connected transformers do not necessarily need to be grounded.
An example of grounding of instrument transformers is given in Appendix G. 11.3 Auxiliary circuits
The auxiliary power supply inside the protection device can be grounded or not. If the device requires single-pole grounding, the auxiliary power supply and the internal auxiliary voltage (circuit) should be isolated, for example using a DC/DC converter. An example of grounding of auxiliary circuits is given in Appendix K. 11.4 Screenshots
In order to reduce the influence of interference, the metal shielding layer of the control (measurement, signal indication, etc.) cable should be grounded. For high-frequency, special attention should be given, see Appendix E.
12 General performance and test requirements
12.1 Test requirements
The test current and voltage on the primary side should be sinusoidal and meet the following requirements. a. The difference between each voltage of a multi-phase symmetrical system (the voltage between any two phases and between each phase and the neutral point) and the average value of these voltages should not be greater than "%.
b. The difference between the phase current and the average value of the system current should not be greater than 1%. c. The phase angle between each current and its corresponding relative neutral point voltage should be the same, and the allowable error should be 2° electrical angle. In addition, the test equipment should be able to simulate the actual primary system fault conditions and provide the required current value and the required DC transient component value.
12.1.1 Method
In the following cases, it is allowed to use the method of applying current and voltage on the primary side of the instrument transformer to simulate: secondary current test. a , input from an independent power supply to simulate load bias, etc. b. Tests at frequencies other than the rated frequency should provide the relationship between the secondary test method and the input test method that has been verified at that frequency.
In other cases, it should be handled in accordance with the agreement between the manufacturer and the user. 12.1.2 DC transient component
For all through-fault tests and internal fault current tests (see 13.1.2.2 and 13.1.2.3), the time constant of the DC transient component in the test circuit should be the maximum value given by the manufacturer for specific test conditions. 12.2 Performance and Test requirements Unless there is an agreement between the manufacturer and the user, individual components may be sufficient: a. temporarily modified to simulate other test conditions; b. temporarily omitted, and its function is reflected by some other means, which can show that the characteristics of the omitted components are non-critical.
Components made for type tests shall comply with the following requirements: 12.2.1 Relays
..comGB/T14598.8—1995
Relays shall be of specified models and shall be set to the setting value that can obtain correct performance within the entire specified range. The characteristics of these relays shall be specified or refer to the relevant parts of TEC.255 . 12.2.2 Current transformers
The performance of current transformers shall comply with the relevant provisions of ISO 10945 or the corresponding national standards. These standards also provide guidance on the use of current transformers of various grades and shall provide the characteristics required by the protection system as specified by the manufacturer. Low reactance current transformers are allowed to have special pre-test windings (see 12.1.1). If the transformer is a high reactance type, the actual transformer should be used. Otherwise, the manufacturer and the user should agree separately to use low reactance current transformers. According to the manufacturer's opinion, in order to maintain the effective resistance of the secondary winding, the number of turns of the primary and (or) secondary windings used for the test may be different from the number of turns specified in the design. The transformer is still in the category of low reactance transformer and the secondary voltage remains unchanged. In particular, when using a small current transformer, its secondary excitation curve and residual magnetism coefficient should also be consistent. The test should be carried out under appropriate ratio and secondary overcurrent multiple. 12.2.3 Voltage sensor
The performance of electromagnetic voltage transformers shall comply with IEC186 or corresponding national standards. And have the durability required by the protection system as specified by the manufacturer.
Note: Under certain conditions, the current 1EC186 stipulates The transient performance of the current-carrying transformer is not appropriate as the basis for the rapid protection system (especially the rapid protection relay). Any restrictions should be negotiated between the manufacturer and the user. 12.2.4 Other auxiliary equipment
Auxiliary equipment includes intermediate current inductors, integrated transformers, stabilizing resistors, rectifiers, resistors, capacitors, sensors, etc. The performance of the auxiliary equipment should be consistent with the characteristics required by the protection system. Any special precautions in the wiring should be specified by the manufacturer. 12.2.5 Communication channel characteristics
Where currents at each end of the protection system are compared through pilot wires at the power system frequency, the channel characteristics shall be simulated in such a way as to represent the resistance of the pilot circuit and the distributed capacitance and/or inductance associated therewith. When pilot wire monitoring is part of the protection scheme, the test of the complete installation shall also include this part. Other communication channels, such as high frequency channels through power lines or ultra-high frequency channels by microwave communication, shall be simulated with due consideration of propagation time and attenuation.
12.2.6 Lead burden of current transformers, voltage transformers and capacitor voltage transformers Lead burden is expressed in terms of resistance. The manufacturer may specify the total resistance expressed as the sum of the resistances of the lead wires and the transformer secondary system. 12.3 Manufacturer's specification of the performance and characteristics of a protection system In accordance with 13.1.1.2, the manufacturer shall demonstrate that the parameters of the protection system being tested comply with the corresponding provisions of this standard. The tests shall determine that the application range specified for the protection system and/or the use of the components in the range of characteristics published by the manufacturer are reasonable. The manufacturer shall specify the characteristics of relays, current transformers and voltage transformers and the auxiliary devices used and, where relevant, the characteristics of the leads and the burden of the leads between the components used. Other characteristics may be limiting factors, such as the maximum voltage on the leads, and shall be specified by the manufacturer. Based on the results of the type tests, the manufacturer may specify the performance of the protection system in accordance with the following items: · Sensitivity · Determined in accordance with 13.1.2.1; · Action time · Determined in accordance with 13.1.2.2
| Stability limit · Determined in accordance with 13.1.2.3. 13 Tests
13.1 Type tests
13.1.1 General requirements
The various type tests specified in this clause are carried out under the condition that the components meet the relevant requirements of the corresponding technical specifications. ..comGB/T14598.8—1995
The protection system shall be subjected to a complete set of type tests together with the relevant components. These components can be the components themselves or simulated components (such as current transformers, voltage transformers, circuit breakers, etc.), which may be provided by several manufacturers. This test is usually performed once by the manufacturer of the protection device.
If major design changes are made to the protection system, the type test should be repeated. In this case, some items of the type test can be omitted.
Except for the test items exempted from 13.1.1.1 and (or) 13.1.1.2, each protection system should be tested in accordance with 13.1.1.1~13.1.1.2.
13.1.1.1 Parameter test
In the type test, in order to determine the future performance of the protection system, all characteristics of the protection system that affect its performance should be studied, and the exact relationship between all parameters and performance can be determined. If the parameters of the special application of the protection system have been shown to obtain satisfactory results by the above relationship, only the component part of the protection system can be tested, and no further type test is required. 13.1.1.2 Special tests
When special tests are carried out, it is only necessary to demonstrate that the protection performance is satisfactory for the specific application requirements. 13.1.2 Performance tests
This clause includes tests of sensitivity, operating time, stability and short-time ratings. All tests shall be carried out at agreed or specified settings. 13.1.2.1 Sensitivity of current-operated protection systems If it is to be determined that a particular relay has a sensitive performance, the protection system shall be type tested in accordance with the requirements given below. The test current shall be gradually increased until the relay operates. For systems involving pulse starting, or systems related to the rate of change of the measured electrical quantity or its transient response, the method used to determine the sensitivity shall be agreed between the manufacturer and the user. It is reasonable to test the sensitivity using the following types of faults. - Phase to ground:
- Phase to phase:
- Phase to ground 1.
Note: 1) This test method and the scope of application shall be a matter for agreement between the manufacturer and the user. For protection systems whose sensitivity varies with phase-to-phase and phase-to-earth faults, the above test shall be repeated for different phase combinations unless the sensitivity can be determined mathematically. For differential systems where the sensitivity is the same at all terminals, the sensitivity of each terminal may be determined by applying a fault current at any terminal. In the case of terminals with significantly different sensitivities, the sensitivity of one terminal to a fault shall be determined by applying a fault current at each of the other terminals, unless otherwise agreed. In addition, when necessary, the sensitivity shall be determined by applying a fault current from each terminal simultaneously. For differential systems with load bias characteristics, the maximum sensitivity shall be determined when the through current is zero and the minimum sensitivity shall be determined at a current equal to the rated current of the protection scheme or a higher current agreed upon by the manufacturer and the user. Repeated measurements of the sensitivity shall be made for the fault types that give the maximum and minimum sensitivities as determined above in this clause. When the differential system is applied to circuits with three terminals or more than three terminals: a. The maximum sensitivity shall be determined with the minimum number of unloaded shunt current transformers agreed upon by the manufacturer and the user; the minimum sensitivity shall be determined with the minimum number of unloaded shunt current transformers agreed upon. The manufacturer specifies that the minimum sensitivity shall be determined by a test in one of the following ways:
Use the correct number of current transformers,
Use less than the correct number of current transformers, and replace the other current transformers with equivalent shunt impedances: b.
For systems where the extrapolation method can be applied, use less than the correct number of current transformers, but the influence of the remaining current transformers shall be calculated.
Note: For the fault conditions mentioned above, the applied current and load bias can be limited respectively (according to the test conditions specified in 13.1.2.1) to obtain the maximum and minimum sensitivity. 13.1.2.2 Operating time under transient conditions GB/T 14598.8--1995
The operating time shall be measured under reference conditions (where possible, based on the relevant parts of IEC255). According to the relevant provisions of IEC55 applicable to the system under test, the operating time of the protection scheme under one (or several) currents applied based on the rated operating performance shall be specified. If necessary, in order to determine the possible saturation effect of any current transformer, the operating time shall be measured under the specified maximum fault current and (or) minimum fault voltage under the fault conditions in the area. The following secondary currents shall be used to measure the operating time: AC steady-state current
The operating time shall be measured three times with a fault current without DC transient components, and the operating time for each measurement shall be recorded. h. AC current with dc transient component The fault current with the maximum dc transient component is applied by a phase closer twice, while the phase of the secondary current varies within 180°. The operating time is the longest operating time measured at each time. The time constant for determining the dc transient component of the secondary current depends on the specified application. Its actual value is specified by the manufacturer (see 13.1.1.2). Unless otherwise specified, any auxiliary excitation quantity shall be the rated value. 13.1.2.3 Stability of protection system
The requirements for stability tests in the following clauses are related to differential and phase comparison schemes. The current with the maximum dc transient component is applied three times by a phase closer, while the phase of the three currents shall vary within 180°. The time constant for determining the dc transient component of the secondary circuit depends on the specified application (see 12.1.2). Its actual value is specified by the manufacturer.
The duration of the applied phase test current shall be not less than 0.2 s or twice the specified operating time of the protection, whichever is greater. The effective value of the symmetrical component of the test current shall correspond to the rated stability limit. If the current transformer is saturated in the steady state or transiently, the stability test of the system must be carried out when the current intensity is below the rated stability limit.
It is reasonable to test the stability according to the following fault current distribution: phase-to-earth fault:
phase-to-phase fault;
three-phase fault;
zero-sequence current.
Note: Other cases are possible, such as the current distribution in any three phases being 2:1, 1, or magnetizing inrush current. For the stability of other types of protection than transformer protection, it may be necessary to consider the magnetizing inrush current caused by switching, such as feeder protection. For this or other special cases (e.g. fault conversion), the manufacturer and the user shall agree on appropriate tests). 13.2 Acceptance test 1
This test is carried out within the manufacturer's premises. The test size shall be agreed between the manufacturer and the user. 13.3 Commissioned test 2
This test is carried out in the user's plant and is generally carried out before the plant and station equipment protected by the protection system is put into operation. The commissioned test items are agreed upon between the manufacturer and the user. Where appropriate, the following tests should be carried out on the protection system. 13.3.1 Instrument transformers and wiring
Instructions for use:
1:Acceptance test is equivalent to the exit test.
2 Commissioned test is equivalent to commissioning test. www.bzxz.net
GB/T 14598. 8—1995
Continuous (power-on) test and insulation test of current transformer and (or) voltage transformer circuit including the connection between transformer and relay.
13.3.2 Instrument transformer characteristics
Check the instrument transformer characteristics under the specified value 13.3.3 Grounding
Check the grounding of secondary winding, auxiliary circuit, etc. 13.3.4 Power supply, etc.
Check the power supply, fuse, small air switch, etc. 13.3.5 Alarm system
Alarm system test.
13.3.6 Setting value
Test of actual setting parameters.
13.3.7 Tripping circuits, etc.
Tests of tripping circuits, including circuit breaker operation. 13.3.8 Secondary test
Tests may be made using load current, other currents (e.g. generator circuits) or primary input test equipment. This test may be used to check the correctness of the ratios and relative polarity between current transformers in a differential system, or between current transformers and voltage transformers in a directional protection system, or to check the correctness of pilot line communication channels. 13.4 Operation test
This test should be carried out periodically.
This test is not as comprehensive as the commission test, but the characteristics of its main relays, logic circuits and tripping circuits are checked. It is generally not necessary to measure the characteristics or polarity of instrument transformers.
Input circuit
Note: 1) From other protection systems.
Avoidance circuit
2) To other tripping and closing circuits
GB/T14598.B—1995
Appendix A
Protection system diagram
(supplement)
Communication
Protection system
Relay
Self-operated or no relay)
Door-activated reclosing circuit
Auxiliary power supply circuit device
Fantun pool
3) TC41 (SC41A/SC41B) has been withdrawn and replaced by TCS4 and TC95 respectively. Appendix B
Tunnel and circuit breakers
Effect of the characteristics and transient response of current transformers on the performance of protection devices (supplement)
81 Overview
Circuit breakers
The performance of protection systems (operation return value, operation and return time, stability to through currents, etc.) is usually affected by the characteristics and transient response of the instrument transformers.
For common types of protection devices (e.g., for all distance protection), it is not possible to specify the type, characteristics and performance requirements of the instrument transformers.
For a given type of protection device (e.g., a given distance protection), the manufacturer of the protection device should coordinate the design of the current transformer, input filter, etc. with the characteristics and transient response of the instrument transformers. B2 Current Transformer
Due to the initial residual magnetism and (or) transient magnetic flux of the core, the transient saturation of the current transformer causes large waveform distortion and zero-crossing displacement of the secondary current, which may lead to deterioration of the performance of the protection system, such as: increased measurement error, increased action value, increased action time, protection expansion beyond the range, action identification error (for out-of-zone faults), output contact jitter, etc. Some types of protection devices may be very sensitive to transient saturation, while other types of protection devices may be insensitive or very insensitive to transient saturation. The core of the current transformer has a small air gap, which reduces the residual magnetism coefficient to a lower value (less than 0.1). The core of the current transformer has an atmospheric
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