GB/Z 18039.5-2003 Electromagnetic compatibility environment - Electromagnetic environment of low-frequency conducted disturbances and signal transmission in public power supply systems
Some standard content:
G#:Z 18039.52003/IEC 61000-2-1:1990 This guidance technical document is equivalent to IE6130021, 1990 Electromagnetic Part 2: Environment Part 1: Environmental description of the public power supply system to reduce the interference and signal transmission environment. The purpose of this guidance technical document is to summarize the detailed information of the public power supply system that is expected to perform various types of services, and is a reference document for the relevant standard negotiation performance compatibility level values. This guiding technical document is Part 5 of the "Electromagnetic compatibility standard" and includes the following categories: GR/7.18039.1-201 Classification of electromagnetic compatibility environments GB/218039.2-2530 Electromagnetic compatibility environment 1 Evaluation of the level of low smoke interference emission of industrial power supply equipment GB/T18039.3-2000 Magnetic compatibility environment for public low voltage power supply systems GB/18039.4-2000 Electromagnetic compatibility environment for public low frequency power supply systems GR/7.18039.5-2003 Electromagnetic thermal conductivity of public low voltage power supply systems High voltage power supply system conducts potential through the signal transmission of the electromagnetic compatibility environment of various environments shielding (to be formulated) This standard technical document is for reference only. Any suggestions and opinions on this general guide technical document shall be submitted to the standardization department of the State Council for registration.
This guide technical document is proposed by the State Economic and Trade Commission for the implementation of this guide technical document. The National High Voltage Compatibility Standardization Technical Committee (CSBTS/TC246) is responsible for drafting this guide technical document: Wuhan High Voltage Research Institute of the State Electric Power Company. The drafting parties of this guide technical document: Fang Baoquan, Gongqi, Luohong, Zhang Chong, Zhang Guangzhou, Yang Shuhui, Lang Wei. GA/7.18C39.5—2003/1EC 61000-2-1:199CIEC Introduction
This document is part of the IEC610(series of standards, which consists of the following: Part 1: Overview
General description (topic, basic principles>
definition, technical specifications
Part 2: Environment
Description of the environment
Classification of environmental parameters
Compatibility levels
Part 3: Limits
Emission limits
Immunity limits (when they are not part of the product committee's responsibility) Part 4 Test measurement techniques
Testing techniques
Part 1: Installation and installation guidelines
Mitigation methods and installation instructions
Part 6: General standards
Part 9: Each part is further divided into several sub-parts, which are issued as international standards or reports. t||1 Scope
GB/?.18039.52003/IEC61000-2-1.1990 Electromagnetic compatibility environment
Electromagnetic environment of low-frequency conduction and signal transmission in public power supply systems
The guiding technical document involves the frequency of 10*Hz and above, and the power grid signal transmission is more generally conducted. The compatibility level of systems with different voltage levels is given in GT/TE80.39.3IFC6000-7-2). This guiding technical document does not apply to the application of compatibility level assessment, such as the evaluation of internal interference emission of the proposed equipment, because this must take into account other cumulative parameters such as impedance that vary with frequency: This guiding technical document does not judge the standards for the immunity level of the relevant product committee, but only provides guidance. This guiding technical document focuses on the following aspects: 1. Spectral effect, voltage passive:|| tt||Voltage sag and short-time power supply
-Central voltage imbalance:
Power grid signal transmission:
-Power frequency change:
-DC basis.
Technical guidance documents provide information on various types of environments that may occur in the public power supply system in the future, and are reference documents for the relevant network compatibility level values.
2 Normative reference documents
The clauses in the following documents are adopted by The references in this technical guidance document constitute the terms of this technical guidance document. All the subsequent revisions (excluding errors or revisions) of the referenced documents do not apply to this technical guidance document. However, all parties are encouraged to study whether the latest versions of these documents can be used according to the actual situation of the technical guidance document. The latest version of the referenced documents is not applicable to this technical guidance document: GB156 Standard Electric Standard (G156--1993, q:G 938: 198): /T5-195E Self-magnetic penetration terminology (idtC6005051>: 190) (H1742. Limitation of voltage fluctuations and flashover in low-voltage common power systems for equipment with rated current not exceeding 16A 6B17625.21999.id: IEC61099-3-3, 1994) GB/18U39.3 Power supply environment Public low-voltage power supply system low-frequency conduction mode and signal transmission penetration level (G/T18039.—2003.1EC:61000-22,1990IDT)1E6C145 Semiconductor terminal
IEC61UJ0-4-15 Flash tester performance and design frequency specification 3 Terms and definitions
(B43 Non-confirmed text and the following. This guidance technical document is not applicable, 1
0B18039.5——2003/[EC61000-2-1,19903. 1
Electromagnetic compatibility (EMc) The ability of a device or system to work normally in its electromagnetic environment without causing unbearable electromagnetic disturbance to anything in the environment.
1.7J
(electromagnetic compatibility) in GB/T4565_995 is the maximum electromagnetic disturbance level expected to be applied to a device, equipment or system working under specified conditions. Note: The electromagnetic compatibility level is not the absolute maximum level. The possible rate exceeds [.15 in G/T 4965-1]
electromagnetic flux finds any magnetic phenomenon that may cause the performance of the device or system to deteriorate, or produce harmful magnetic phenomena with or without living substances.
The detailed electromagnetic disturbance may be insufficient for electrical operation, useless signal format changes of the medium itself, [1.5 in G/T 4365-1995]
pure level diglurbsDceleveli (defined in B4365) is the value of the electromagnetic disturbance measured according to the prescribed method. 3.5
Interference limit Lmltordlsibace
corresponds to the specified measurement of the amount of interference allowable level, ICB/T4365-1995 3.9]
Immunitylevel
will be the minimum interference level when the electrical immunity is applied to a certain device or system so that it can work normally and maintain the required performance.
[GR/T13G5-1995 3.74]
(Electromagnetic) Susceptibility (clectromaetie) susceptibility is the ability of the device, equipment or system to avoid performance degradation under the condition of electromagnetic interference. Note: Susceptibility is true immunity.
[G43551995 1.217
4] The purpose of specifying the level of interference tolerance is to form a level of interference tolerance. It can be seen that it is a reference value. With the help of the compatibility level, the system status and the current disturbance level of various types of equipment can be coordinated: and in the actual application, the maximum interference level with a certain probability in the self-protection environment of the device is set. In order to avoid causing -: the reference value related to its average level must be selected. In some cases, the level must be selected to be sufficient for several interference sources (such as harmonics, and in other cases, it must be caused by a single weak interference source (such as non-reproducible heart rate drop). It is emphasized that the screening level is not a fixed value, it varies with the starting point and time. In this regard, the statistical distribution of the interference must be considered.
GR/7.16039.5—2003/1EC 61000-2-1,1990 The level of interference can be derived from actual network measurement results or possibly from theoretical studies. The uncertainty of the level of interference often makes it difficult or even impossible to determine the actual maximum level of interference that may occur rarely. Most equipment will at least be subject to this maximum value, so it is generally uneconomical to define the maximum level as the compatibility level. Therefore, the appropriate compatibility level is not determined by the "maximum value" of the interference, but by determining the interference level that will be exceeded in a few or very few cases - but by making the compatibility level cover at least the right situation. The immunity level of the equipment should not be too high. The immunity level must be verified by appropriate tests. The relevant professional technical committee is responsible for determining its value and test frequency. The sensitivity level of the equipment is the level that affects the performance of the equipment and should be equal to or higher than the immunity level determined by the test: taking into account the long-term use conditions and the specified immunity limit, the sensitivity level should be determined appropriately. The sensitivity level may need to be studied using statistical methods, especially for devices that are usually not connected to each other and are temporarily connected to the public power supply system for independent use. The compatibility level is used as a reference value for no-derating operation. Figure 2 shows the relationship between different interference levels with statistical characteristics. For special or independent systems, such as those serving a particular user and equipment, other interference levels may be allowed: 5 Please speed
5.1 Description of the phenomenon
Noise is a positive or sinusoidal current with a frequency of an integer power supply system frequency (such as 50Hz). Latent interference is generally caused by equipment with practical voltage/current characteristics. Such equipment can be considered as a cross-wave current source. The wandering current from the non-network source generates a residual voltage drop in the network impedance. This phenomenon is simplified in Figure 2. In fact, the currents in different situations are added. Due to the influence of the reactive load (the power compensation capacitor terminal) connected to the cable, parallel and series data can appear in the power grid, and some even become negative during operation. The voltage will increase if the voltage is not properly connected. 5.2 Generation of harmonics
The harmonic currents generated by power generation, distribution and distribution equipment are small and low in level; the currents generated by industrial and civil loads are relatively large, and the level of harmonics is relatively high: Usually there are a few power grids that generate significant harmonic currents, and most of the single harmonic power generated by these equipment is low.
The sources that generate significant harmonic currents in the power grid are as follows: 1. Solar power equipment with phase selection: 2. Uncontrolled rectifiers, especially rectifiers with passive filters (such as those used in televisions, inverters and ballasts). Because these harmonic sources have the same phase and there is no compensation in the power grid, the harmonic level generated by the source can be stable or variable, which depends on the operating mode. 5.2.1 Generation, distribution and distribution equipment
The following types of equipment include This includes equipment powered by the public power grid, especially generators, transformers, and recently adopted stop compensation generators and rectifiers.
It is impossible to obtain pure strong harmonics in the design of the generator. The generator generally behaves as a harmonic source: under the condition of proper selection of the number of slots per pole, line node embedding, etc., these harmonic slopes can be ignored, that is, the almost sinusoidal shape can be guaranteed. The characteristic is that the transformer will produce secondary and higher harmonics.
The transformer is caused by the lack of core and the transformer voltage. 5.2.2 Industrial load
Industrial loads may be a source of harmonics with a considerable level of spectral variation, including power converters (rectifiers), boilers, insulators, etc. With the increase in the number of power electronic equipment and the increase in the number of single-phase transformers, there is a considerable impact on the interference level of the power grid. GB/%180 39.5—2003/1EC61Q00-21.1990 According to the theoretical analysis of the current spectrum, the number of harmonics in the characteristic spectrum is: n=pxmll
formula:
n——the number of harmonics in the spectrum;
m—the total integer (1.2.3...)
Of course, it is also difficult to determine the control angle. The power supply voltage is unbalanced, and its impact on the balance of the rectifier bridge is also very important. For example: in the power supply of a 12-pulse rectifier, the 7th harmonic and the 7th harmonic are measured. In theory, the amplitude of the harmonic current of the phase-commutating converter should be reduced according to the following law: I..in
Where:
T,——the amplitude of the nth harmonic current:
1.1.2 harmonic amplitude.
The commutation of the rectifier is not instantaneous, nor is it a real harmonic. The amplitude of the harmonic current is determined by the inductive voltage drop on the inductor of the circuit and the commutation angle. The current in the circuit supplied by the rectifier can be calculated by the following formula:
I = /(—3/).:
where
is the harmonic order. If a very flat DC current is generated, this formula is applicable, and the technical level of the 5th harmonic may need to be higher. When considering the inductive voltage drop at the delay angle, more detailed harmonic current value data are provided in IE6V146. The current can be represented by a harmonic current generator with inductance and damping resistance, and its output harmonics appear as a kind of micro-frequency superimposed on the continuous belt.
5.2.3 Residential loads are low rated for preload, and the loads are used for a long time. The main source of harmonics is the thyristor controlled equipment (dimming lamps, lighting appliances).
TV sets are powered by capacitors with large capacity batteries: The power supply from the power grid contains harmonics.
Non-thyristor controlled loads are used more often. Although the power density of each code may be small, the product effect can cause a high degree of distortion in the power supply.
5.3 The influence of harmonics on the tooth wave is that
The operation of the regulating device is not correct!
Causes malfunction of the wave controller and other telecommunication transmission systems, relays and other possible control devices; causes the motor and other equipment to produce extra noise; and disturbs the telephone.
The effect of the inductor on the power meter is still unclear: the interference phenomenon caused by the inductor on the power and communication lines is discussed in detail, and no specific description is given here. The harmful effects of the equipment can be divided into two types: time or length: 5. 3. 1 Time-dependent effects
These effects are the slow shift of the internal voltage shape when it passes through zero, and the derivative changes and the equipment is released, the control performance is reduced, and the periodic device, the heart rate and the computer are not affected by these effects.
(B/218039.5-2003/EC61000-21:1990) The commercial value of the wave can cause the failure of the wave control receiver and the protection relay. 5.3.2 Long-term effects
The long-term effects are mainly heat, additional consumption and over-efficiency, which gradually lead to excessive deterioration of capacitors and energy converters and even damage to the loop. 6 Harmonic currents
6.1 Description
Between the harmonic currents or liquid currents with the supply frequency as the harmonic frequency, other frequencies that are not multiples of the fundamental frequency can also be observed. They are reduced in frequency or Appearing in the form of a spectrum, the effect of interharmonics is not significant, so there is no need to consider the obvious addition of interharmonics.
6.2 Generation of interharmonics
The source of interharmonics can be found in low-voltage power grids or medium- and high-voltage power grids. The interharmonics generated by low-voltage power grids will also affect the nearby equipment; the interharmonics generated in medium-voltage/commercial-voltage power grids will flow into the low-voltage power grids powered by them. The main interharmonics are transformers, transformers, non-step-by-step transformers, induction motors, and welding (in medium-voltage power grids, they are connected to medium-voltage high-voltage power grids!). Even if there is no clean interharmonics, it will also add low-voltage noise to the low-voltage waveform; in a broad sense, the signal quality of the power grid can also be used as a reference for the same case, and it is better to divide them into different parts. 6.2.1. Frequency converter
Frequency converters convert the grid voltage into AC power with a frequency lower or higher than the grid frequency. They are composed of two parts, namely, an AC-follower and an AC-inverter. When the voltage is adjusted by the output frequency of the frequency converter, if there is a back-wave current in the input current, a back-wave voltage will be generated in the grid voltage: the frequency converter is mainly used for adjustable power supply, and the speed is reduced. Small power equipment below tens of kilowatts is connected to the low-voltage grid. Large power equipment is connected to the grid through a special transformer. Similar frequency converters are also used to power medium-voltage furnaces.
Different forms of frequency converters have different characteristics. The modulation rate and harmonic inter-frequency are given by the following formula: f[(Xm)±Xf±XxF
wherein:
—pulsation number of the inverter;
—pulsation number of the frequency converter
h-——0,.2,3 integer;
F——output frequency:
f-fundamental frequency of the power supply voltage (Hz or 60Hz); The harmonic inter-frequency produced by the product of m and m can be obtained, and these can be combined with the above to obtain: 6.2.2 Frequency converters are high-power electronic inverters (usually 1 watt, they absorb symmetrical one-phase power from the power system and produce a low-frequency power lower than two-phase) for large low-connected motors. They consist of two or more controlled rectifiers connected in a bridge configuration. The calculation formulas for harmonics and inter-harmonics are the same as for static rectifiers. 6.2.3 Quasi-stepped series inverters
When the induction motor deviates from the rated state, the step-by-step series inverter controls the motor's transfer and reduces losses. When the resistor connected to the output terminal of the on-line motor is connected, a transformer connected between the output terminal and the motor stator line is used to replace the resistor. In general, the inter-harmonics of the enterprise are low. 5
GB/Z 18039.5—2003/[FC:61000-2-1:19906.2.4 Induction motor
In the induction motor, there is a magnetic field in the stator and rotor, which produces irregular induced current (which may be related to the core and the ground), which may cause low-frequency fluid in the core network: At normal speed, the induction frequency of the motor is FmH? (MIHz constant range, but during starting the entire explosion pot range below 2000Hz is taken. Installed in long (greater than 1km> overhead line) the end of the voltage is full for the motor to be affected by the technology. The measured interharmonic voltages have reached 1% of the rated voltage. In a few cases, these interharmonic voltages will disturb the ripple control receiver. 6.2.5 Electric welding machine
The electric welding machine will produce a continuous broadband spectrum: the welding process may be an intermittent process, and the duration of each welding change varies between 1 second and several seconds
Electric welding is mostly connected to the low-voltage power grid. Regarding the interharmonic medium voltage generated by the electric welding machine, no measurement results can be provided at present. However, due to the high interharmonic points and high power of the welding process, the interference of the power supply network must be very low to avoid the influence of flicker interference. Therefore, the grid impedance is similar to the suspension to reduce the interharmonic voltage. 6.2.6 Electric furnace
Due to the arc furnace The irregular current input produces a continuous but irregularly changing harmonic spectrum. These devices have a large rated capacity (5nMVA ~ 10MVA) and are usually connected to the medium voltage / low voltage. To avoid large power fluctuations and flashovers, the grid energy expansion should be small and the generated power is also small. The high-frequency current appears at the beginning of the refining process. The typical value is still under study. 6.2.7 Background noise
The background noise appears as a Gaussian wave with a continuous regular spectrum between the harmonics. So far, few studies have been conducted. Typical positive voltage levels are shown in the following figure: 4mV to 50mV (about 3.02% of U) when measured with a full-bandwidth filter of UFLs; 20mV to 25mV (about 0.1% of U) when measured with a filter of 3H bandwidth. 6.3 The response of the current
The influence of the discrete sequence frequency on the control receiver is caused by the interference of the discrete sequence frequency. This influence is observed by the induction motor and the arc furnace. If the design is not done properly, this influence will not be produced. The flicker effect will also be manifested at high frequencies near the base. These frequencies can be used to fluctuate the current amplitude. If the flicker frequency is close to 1C [7.3.1], this phenomenon will be particularly noticeable. The research on this phenomenon is still ongoing. 7 Voltage fluctuations
71 Phenomenon description
Voltage fluctuations can be described as a series of random voltage changes (see Figures 3 and 4) from the periodic change of the voltage line to the voltage line (see Figures 3 and 4). The range of its changes does not exceed 1.10% of the voltage given in GB156: the voltage fluctuations must be clearly distinguished from the false changes caused by the gradual change of the load in the same power grid within the same maximum limit of ±10%.
Voltage sags and short-term medium It is a rare occurrence, and its voltage is between 1°C and 130°C of the nominal voltage. It is mainly caused by the action of the voltage protection device (see Chapter 8). Voltage fluctuations have several types, which can be divided into the following types (3/T17625.2): Type h: a series of irregular step voltage changes with equal value, such as single input of power supply (see Figure 5); Type h: a series of irregular step voltage changes with equal value, The degree of rise or fall may be different, such as multiple loads (56):
Type C: The change is different and not all are step-type voltage changes, such as non-resistive loads (Figure 5c)) Type d: A series of random or continuous voltage fluctuations, such as periodic random load changes (d)) Note that two or more voltage changes occur simultaneously within a total period of less than 3 hours. Only one voltage fluctuation is used. 6
GB/Z 18039. 5—2003/IEC 61000-2-1:1990 The type of voltage fluctuation can be inferred from the storage characteristics or detected by a device. 7.2 Generation of voltage fluctuations
In low-voltage power grids, household appliances are an important source of voltage fluctuations. Most of the time, each appliance will only affect a limited number of users. Generally speaking, the main source of voltage fluctuations is industrial loads, welding machines:
rolling mills:
bending wells (or electric motors with variable loads):
arc welding equipment.
When the capacitor is disconnected (or removed) or when operating a large load, the resulting series voltage fluctuations have similar properties.
It should be noted that these fluctuations caused by industrial loads will affect most users in the same power supply. The operating characteristics of these loads vary from continuous to less frequent use. Because the range of power line interruptions in the public power grid is wide, the voltage fluctuations from the substation are very important. The situation at the end of the feed-in circuit varies greatly. 7.3. The influence of voltage fluctuations
Since the voltage amplitude does not exceed ± %, most equipment cannot resist this kind of fluctuation. The main cause of the voltage fluctuation is flicker, that is, the fluctuation of the lamp charge (it is important to note that the characteristics of the filament cannot actually be changed). The frequency of this phenomenon is related to the amplitude, frequency and duration of the voltage fluctuation. However, there are some equipments below which the flicker is invisible. Some equipments, such as the time constant of the generator, are almost unaffected by the voltage fluctuation. Other equipments, such as motors, electronic control devices and computers, are naturally sensitive to the voltage fluctuation. In this case, the fluctuation is not as good as 0. Hz--30 H2 band thermal spectrum, usually the impact of individual frequencies can be evaluated by internal frequency measurement (see E610U-4-15). This amplitude modulation is basically the ratio of the central power supply network installation point impedance to the interfering equipment impedance. (The short-circuit capacity of the power supply network is inversely proportional to the modified capacity).
7.3.2 Cascade voltage changes <such as welding machines, motor starting, capacitor bank operation, etc.! In this case, the unpleasant event is mainly related to the voltage change with the rate of change. Daily voltage sag and short power interruption
8.1 Phenomenon description
A voltage sag is a voltage drop at a point in the power system, which is followed by a short period of time of half a cycle to a few seconds and the voltage recovers. A short power interruption is a power failure of less than 1 mil: a short power interruption can be a drop of 0.00 and a voltage drop of 8.1.1 The voltage sag of type
is defined as the voltage difference between the positive voltage during the voltage dip and the nominal voltage of the system (see Figure 6). Assuming that the voltage sag can be expressed as a percentage of the nominal voltage,
is a continuous small voltage sag of constant value and duration. Complex voltage sags (see Figure 6) can be characterized by two or more groups of voltage sags. However, such complex voltage sags are rare: therefore, in actual use, they can be characterized by the maximum amplitude and duration. 8.1.2 Drop amplitude and duration
When the voltage at a certain point in the system drops below the nominal voltage, it is not considered a voltage dip, because this is a voltage fluctuation caused by a series of slow positive changes (caused by a gradual change of ten negative impulses) and ten rapid single negative changes (see the most in 6
GA/7,18039.5-·2003/IFC 61000-2-1:1990 Voltage variations:
Voltage variations with a duration of less than half a cycle are not considered to be a characteristic of the AC power supply. Voltage variations with a duration of less than half a cycle are considered to be a phenomenon. It must be understood that a certain number of positive dips are inevitable in the power supply network, and for most equipment, there is a limited number of small dips that can be tolerated. However, these two parameters, namely the dip and the duration, cannot actually be limited in the power supply network. All dips between 1% and 0% and all durations longer than half a cycle are possible. For the given network The voltage drop and short-term interruption caused by the voltage sag may be caused by the switch failure, which may cause the protection device (including the momentum gate) to operate. These events may occur in the household building or the public power supply network. 8.3 Voltage supervision and torque response to power supply interruption warning and power supply interruption equipment connected to the power grid: the following abnormal operating conditions: discharge lamp dance chicken fire
--switching device. 7 malfunction,
motor speed change or stop:
relay jump:
-computer! The measurement device with electrical equipment has a fault drop and the calculation is different! : The synchronous electric motor is operated in an inverter mode. If there is a phase change failure in the circuit, the equipment may take up to several hours to restart, which will make the above situation worse. 9 Voltage unbalance
9.1 Description of the phenomenon
Voltage unbalance refers to the situation where the voltage amplitude of one phase is different, or the phase is asymmetrical (that is, the phase is not the normal 120°), or when both exist.
The degree of unbalance is generally determined by the ratio of the negative sequence (or zero sequence) component to the positive sequence component. The negative sequence (or zero sequence) in the power grid is mainly determined by the technical 9.2 Voltage imbalance is the main cause of voltage imbalance. In low-voltage power grids, single-phase loads are almost only connected between phases and the neutral point. They are mostly evenly distributed in three-phase networks. In the commercial network, single-phase loads can be connected between phases or between phases and the neutral point. For some single-phase loads in electrification, the voltage imbalance degree can be calculated by the following formula: Three-phase voltage imbalance (the ratio of the single-phase average voltage in the three-phase grid to the average voltage of the single-phase load connected between two phases) is actually equal to the ratio of the load rate to the two-phase short-circuit rate. The negative sequence voltage is transmitted from a lower voltage grid to a higher voltage grid. Any gain in the direction from higher voltage level to lower voltage level is related to the presence of a two-phase rotating machine with a balanced load: 9.3 Effects of voltage imbalance
The impedance of the three-phase machine is proportional to the impedance between its starting element: the parts previously operating on an unbalanced load will draw unequal currents, which are not half the current drawn by the supply voltage. Therefore, one phase current may differ significantly, and the heating caused by the addition of the current to that phase or two will only be partially offset by the reduced heating in the other phases: the resulting temperature rise of the machine is greatly increased. The most serious form of unbalanced current is the interruption of one phase, which quickly leads to the destruction of the motor. Especially for large-capacity and relatively large-displacement motors and generators, the current is equipped with protection devices to detect this situation and eliminate the current. If the current is unbalanced, the "single-phase" protection device can respond to the unbalanced current and disconnect the motor. In a multi-phase inverter, since each phase input voltage takes turns to provide DC power, the multi-phase inverter will also be affected by the uneven current, resulting in undesirable ripple on the DC side and undesirable harmonics on the AC side. Since the unevenness mainly affects the output potential, it causes the machine to heat up, so the unbalance that lasts for a period of even more than one minute is acceptable.
10 Power grid signal transmission system
The public power grid is used to supply power to the same household. Sometimes, public power companies use it for signal transmission. Regarding the signal transmission system itself and its impact on the power grid (load adjustment, meter reading, etc.), it must be guaranteed to have electrical compatibility.
TO.1 Phenomenon description
The signal from 110Hz--500kHz is used in the power grid or part of the power grid to transmit the information from the sending location to one or more receiving points.
The power outage information transmission in the power supply system can complete the following tasks: from the communication center station to the user's equipment, the information is sent to the user at any time: change of tariff, load switching, or the communication center station obtains information through the network or point, such as status indication signals or measurement pins, etc. bzxZ.net
The system that sends information and instructions is called the "output system", and the system that collects and transmits information is called the "reduction system". Various output systems are in operation, while the human system is still under development. 10.2 Generation of power grid signals The power grid signal system that distributes the transmission signals from high-voltage, medium-voltage and low-voltage lines can be divided into the following categories according to the transmission rate or type of the signal: 1) Medium frequency power line carrier system (or low-voltage power line carrier system): The normal signal ranges from 11CHz--200CH, but the normal signal range is 113Hz--50Hz. This system should be installed in the public power grid (in the industrial power grid), and the alarm signal is injected into the high, medium or low-voltage power grid. 2) Medium frequency power line carrier system: The normal signal ranges from 3kHz to 122kHz, preferably from 1kHz to 122kHz. Such systems are mainly for public use: At present, only a few companies are in operation and the signals are injected into the high-voltage power grid. The characteristics of this system are not uniform, but the system uses a non-sinusoidal signal with a power line or wave system without a regular frequency. The new band is 20k11z--50k1z or more. The signal is transmitted to the low positive grid. This system should be suspended in the public power supply of the power supply from the power supply of ... .5ms~3.0a electric giant reduction state (better effect in the zero area of the voltage waveform. To avoid the gradual phenomenon of mountain flash:
"swelling", the notch shape of the dry waveform, the duration is 2)50-"core H fundamental frequency pulse", the duration is half a full wave or one cycle. This system is used to transmit the old signal of the public power grid to the medium or low-frequency power grid. 103 grid value transmission to call the impact of grid value transmission equipment The string stop signal in the low and medium range can be recognized as similar to 1: Cheng Ping less (early signal transmission system up to) Xie 9
GH/18039.5-2003/5EC61000 2.1.1990 The harmonics are pulsed and can affect radio equipment or TV receivers as well as electronic equipment such as electronic regulators, computers, etc. In some cases, this effect can be similar to a change in the effective power supply voltage, detected by voltage drop (flicker). The signals in the radio frequency range mainly cause conducted interference or radio interference in radio equipment. The power grid communication system may be affected by power grid interference, especially by inter-wave and inter-wave interference. It is necessary to consider the influence of the adjacent systems.
11 Power supply frequency variation
11.1 Description of the phenomenon
The current rate of a public power system is directly related to the rotational speed of the generator. The alternating current obtained by a generator separated from the public power system is often the same: under any circumstances, the alternating current is usually in dynamic balance with the generating equipment: therefore, when this dynamic balance is not achieved, there will be a small change in frequency. The size and duration of the change depend on the characteristics of the load change and the response of the generating equipment to the load change. When the power comes from the inverter, the rated power can be determined by the control circuit and then fixed. Under normal circumstances, the specifications of the public power supply system are generally rated specifications with a small bandwidth distributed by the power supply department. In this frequency band, the change of the power frequency is generally limited.
112 Generation of power frequency change
In the public power system, the power capacity is required by the overload demand to keep the frequency change within the specified range. However, under some circumstances, such as a large number of load shedding states, the power change will exceed the rated range. In this case, in order to minimize the loss, some loads should be automatically or manually cut off or the generator generally does not regulate the speed. The power required at a lower frequency is less, so that the loss can be compensated to a certain extent by the lower required power.
11.3 Effect of power supply frequency variation
In the range of the tested products, the cavitation of the motor will have an impact on the accuracy of the rotating motor. For example, the clock will not run correctly and the gear ratio of the motor transmission will not be correct. Its change depends on the speed-torque characteristics of the load. Power supply frequency variation may also affect the filter regulation.
Electric equipment that uses the power supply frequency as a time reference will also be affected. The DC component of T2
is under special consideration.
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