RU49388U1 - COMBINED RELAY PROTECTION DEVICE FOR SINGLE-PHASE EARTH CLOSES - Google Patents

Abstract

The utility model relates to techniques for relay protection and emergency automation and is designed to selectively disconnect lines with single-phase stable and unstable earth faults, including arc faults. The purpose of the invention is the creation of a combined relay protection device, which, when using well-tested methods for the selective determination of damaged connections:

- reduces the likelihood of excessive action of directional protection;

automates the actions of protection controlling the high-frequency components of the current 3I ₀ ;

- provides continuity of action with sustainable OZZ;

- registers single and intermittent short-term emergency zones;

- Has the highest possible sensitivity and speed. The combined device for relay protection against single-phase earth faults contains power direction switches, galvanic isolation blocks and preliminary scaling of the input signals in the form of current and voltage, two comparators, a frequency filter unit, an analog-to-digital converter, two I elements, and a microprocessor control system for output relays and alarm in accordance with protection algorithms. The proposed device can be used to protect against single-phase earth faults at distribution substations 6-35 kV with insulated neutral, at power plants and traction substations of railways.

Description

The invention relates to techniques for relay protection and emergency automation, and is intended for selective shutdown of outgoing from the section of the switchgear 6-35 kV lines with single-phase stable and unstable earth faults (OZZ), including arc.

The known protection device for single-phase earth faults ZZP-1M [Alekseev BC, Varganov GP, Panfilov BI, Rosenblum P.Z. "Protection Relay" M., Energia, 1976. P. 371] [1], containing a matching transformer, a limiting circuit, an alternating current amplifier, a phase-sensitive amplifier and an actuator are directional protection in networks with isolated neutral and selectively operates with metallic and stable arc faults, but in the presence of an arcing reactor, directional protection does not work due to suppression of the main component of the current 3I ₀ , or acts deliberately non-selective during overcompensation. In intermittent arc faults, directional protection also either does not work or works non-selectively.

Known protective device for single-phase earth fault USZ-3M [Shabad MA "Protection against single-phase earth faults" - lecture notes, Department of relay protection and automation of power plants, networks and power systems, 1997. Pages 21, 32-34] and [Shuin VA, Gusenkov AV "Protection against earth faults in electric networks 6-10 kV" - Library of Electrical Engineering - supplement to the journal "Energetik" 2001. P.64] [2] containing a matching transformer, LC bypass filter, RC filter, rectifier, two resistors, capacitor and an electrical measuring device allows substation personnel to determine the feeder with the highest value of the sum of the highest harmonics in the current 3I ₀ by a method of comparison and manually disconnect this feeder, but it only works with a stable single-phase earth fault, it has a long manual process deterioration of the damaged feeder and the need for a large number of control cables from the feeder cells of the switchgear to the installation site USZ-3M.

The closest technical solution is the device - "Microprocessor protection system" [Patent RU No. 22173924 N 02 N 7/26 B.I. No. 26 dated 09/20/2001] containing blocks of galvanic isolation and preliminary scaling of input signals in the form of current and voltage, a shaper of control signals and

diagnostics, a block of frequency filters, an analog-to-digital converter and a microprocessor-based control system for output relays and alarms in accordance with protection algorithms.

The disadvantage of the prototype is the possibility of excessive (non-selective) operation when:

- single-phase earth faults (OZZ) in networks with overcompensation;

- intermittent (intermittent) single-phase arc faults to earth in networks with isolated neutral.

The purpose of the invention is when using well-tested methods for the selective determination of damaged attachments:

- reducing the likelihood of excessive action of directional protection;

- automation of the protection action controlling the high-frequency components of the current 3I ₀ ;

- ensuring the continuity of action with sustainable health protection;

- registration of single and intermittent short-term emergency zones;

- obtaining the maximum possible sensitivity and speed;

- obtaining a wide range of settings in time and in response angle (for directional protection).

This goal is achieved by the fact that in the known device containing blocks of galvanic isolation and preliminary scaling of the input signals in the form of current and voltage, a block of frequency filters, an analog-to-digital converter and a microprocessor control system for output relays and signaling in accordance with protection algorithms, moreover, the group of outputs of the blocks galvanic isolation and preliminary scaling of the input signals in the form of current and voltage are connected, respectively, with the first and second group of inputs block of frequency filters, the group of outputs of which is connected to the group of inputs of an analog-to-digital converter, the group of inputs and outputs of which is connected to the first group of inputs and outputs of a microprocessor control system for output relays and alarm in accordance with protection algorithms, power direction relays, two comparators and two element And, moreover, the microprocessor control system of the output relays and the alarm system in accordance with protection algorithms contains a set of bus drivers, a central processor, a soup examiner, two random access memory devices, read-only memory device, clock, two sets of buffer

registers, mini-display and indicators, keyboard, microprocessor, analogue input-output device, discrete input-output device, driver for communication with automatic control systems and driver for communication with PC, moreover, groups of inputs of galvanic isolation units and preliminary scaling of input signals in the form of current and voltages are, respectively, the first and second groups of inputs of the device, the first, second and third group of inputs and outputs of which is, respectively, the second, third and fourth group of inputs and outputs of the microprocessor th control system of output relays and alarm in accordance with protection algorithms, the first input of which is connected to the output of the first AND element, the first input of which is connected to the output of the power direction relay, the first and second inputs of which are outputs from the output groups of galvanic isolation units and preliminary scaling of input signals in the form of current and voltage, respectively, the second input of the first element And is connected to the output of the first comparator, the first input of which is connected to the first output from the group output s block of frequency filters, the second output of the group of outputs of which is connected to the first input of the second comparator and the first input of the second element And, the second input of which is connected to the output of the second comparator, the output of the second element And is connected to the second input of the microprocessor control system of output relays and signaling according to protection algorithms, the second inputs of the first and second comparators are connected to the circuits of the first and second reference voltages, respectively.

Figure 1 shows the structural diagram of the device.

Figure 2 - characteristic dependence of the response time of the current protection of high frequencies from the current 3I ₀ RF.

Figure 3 is an example implementation of an analog-to-digital Converter.

Figure 4 is an example implementation of a block of galvanic isolation and preliminary scaling of the input signals in the form of current.

Figure 5 is an example implementation of a microprocessor control system for output relays and alarm in accordance with protection algorithms.

6 is an example implementation of a block of galvanic isolation and preliminary scaling of the input signals in the form of voltage.

7 is an example implementation of a block of frequency filters

Figure 1 marked:

1 - block galvanic isolation and preliminary scaling of the input signals in the form of current;

2 - block galvanic isolation and preliminary scaling of the input signals in the form of voltage;

3 - power direction relay type RBM-178/1 or RBM-178/2 or similar;

4 - block frequency filters;

5, 6 - comparators of type 554 SAZ or similar;

7 - analog-to-digital Converter;

8, 9 - elements And type KR1554LI1 or similar;

10 - microprocessor control system of output relays and alarm in accordance with protection algorithms;

11 - a group of current signals of the protected object;

12 - group of voltage signals of the protected object;

13 - current circuit 3I ₀ from the current transformer of the protected object;

14 - voltage circuit 3U ₀ from the voltage transformer of the protected object;

15 - signal circuit of the effective value of the fundamental harmonic of the zero sequence current (3I ₀ 50);

16 is a signal circuit of the effective value of the high-frequency component of the zero sequence in the frequency band from 150 to 650 Hz (3I ₀ RF);

17 - communication bus with ACS;

18 - a group of inputs - outputs for communication with external devices, i.e. inputs / outputs of an analog input-output device and inputs / outputs of a discrete input-output device;

19 - communication bus with a PC.

U _OP1 and U _OP2 - the circuit of the first and second reference voltage.

Figure 2 marked:

3I ₀ HF _max - the largest value of the own capacitive current of any intact connection;

∑3I ₀ VCH - the total value of the capacitive currents of all connections of the section.

Figure 3 marked:

20 - multiplexer, can be implemented on a chip type ADG4288A or similar;

21 - analog-to-digital Converter, can be implemented on microcircuits like AD677AD and REF-01CP or similar;

22 - microprocessor device, can be implemented on a chip type ADSP-2115BP-66 with memory M27C256 or similar;

23 - buffer registers, can be implemented on a chip type 74HC374N or similar.

In figure 4 are indicated:

24 - operational amplifier, chip type QP177GP or similar;

R - resistors type C2-33 or similar;

T - current transformer type TT-1T ... TT-5T or similar;

D - diodes of the type 2D510A or similar;

V1 - transistor type BD135 or similar;

V2 - transistor type BD136 or similar.

Figure 5 marked:

25 - a set of bus formers of the type KR1554AP5 or 74NS244 or similar;

26 - a central processor of the type AT89C52-24PI or similar (to simplify the circuit, a resonator and control circuits are not shown);

27 - supervisor type ADM693AN firm "ANALOG DEVICES" or similar;

28 - a set of buffer registers of the type KR1554IR23 or similar;

29 - mini-display and indicators;

30 - keyboard;

31 - real-time clock type RTC72423B of the company "EPSON" or similar;

32, 33 - RAM type SRM2A256LLCT or similar;

34 - ROM type AT28S256 or similar;

35 - a set of buffer registers type KR1554IR23 or similar;

36 - microprocessor type AT89C52-24PI or similar (to simplify the circuit, the resonator and control circuits are not shown);

37, 38 - devices of analog and discrete input-output;

39, 40 - drivers for communication with automatic control systems and personal computers of the ADM232AAN type by ANALOG DEVICES or similar.

Figure 6 marked:

41 - operational amplifier, chip type QP177GP or similar;

R - resistors type C2-33 or similar;

T - current transformer type TT-1T ... TT-5T or similar;

D - diodes type 2D510A or similar.

7 marked:

R - resistors type C2-29V or similar;

C - capacitors type K73-39 or similar;

L - inductors (inductors) type SMCC firm "FASTRON" or domestic type DM, DPM or similar.

In Fig. 1, they are not shown in detail how they do not affect the operation of the device and are given in the descriptions of the elements, power direction relay 3 circuits and comparators 5, 6 (input circuits 13-16, make contact circuit, power circuits, supports, etc. ) A description of the power direction switch is given in [V.M.Elfimov "Power direction switch" 1966 p. 4-30] [3].

The signals from the outputs of the elements And 8 and 9 are fed to port P1 (not shown in FIG. 5) of the central processor 26 of the microprocessor control system of the output relay and alarm in accordance with protection algorithms 10.

The combined device for relay protection against single-phase earth faults contains blocks of galvanic isolation and preliminary scaling of input signals in the form of current 1 and voltage 2, power direction switch 3, frequency filter unit 4, comparators 5 and 6, analog-to-digital converter 7, elements And 8 , 9 and a microprocessor control system for output relays and signaling in accordance with protection algorithms 10, groups of inputs 11 and 12 of galvanic isolation units and preliminary scaling of input signals in the form of ka 1 and voltage 2 are, respectively, the first and second groups of inputs of the device, the first 17, second 18 and third 19 groups of inputs and outputs of which are, respectively, the second, third and fourth group of inputs and outputs of the microprocessor-based control system for output relays and signaling in accordance with protection algorithms 10, the first input of which is connected to the output of the first element And 8, the first input of which is connected to the output of the power direction switch 3, the inputs 13 and 14 of which are the outputs of the groups of outputs of the galvanic time blocks language and preliminary scaling of the input signals in the form of current 1 and voltage 2, respectively, the second input of the first element And 8 is connected to the output of the first comparator 5, the first input of which is connected to the first output 15 from the group of outputs of the frequency filter unit 4, the second exit from the group of outputs 16 which is connected to the first input of the second comparator 6 and the first input of the second element And 9, the second input of which is connected to the output of the second comparator 6, the output of the second element And 9 is connected to the second input

microprocessor control system of output relays and alarm in accordance with protection algorithms 10, the second inputs of the first 5 and second 6 comparators are connected to the circuits of the first U _OP1 and second U _OP2 reference voltage, respectively, of the group of outputs of the galvanic isolation units and preliminary scaling of the input signals in the form of current 1 and voltage 2 are connected, respectively, with the first and second group of inputs of the frequency filter unit 4, the group of outputs of which is connected to the group of inputs of the analog-to-digital converter 7, g the I / O I / O of which is connected to the first group of inputs and outputs of a microprocessor-based system for controlling output relays and alarm in accordance with protection algorithms 10, a microprocessor-based control system for output relays and alarm in accordance with protection algorithms 10 contains a set of bus drivers 25, a central processor 26, a supervisor 27, two random access memory devices 32, 33, read-only memory device 34, clock 31, two sets of buffer registers 28 and 35, mini-display and indicators 29, keyboard 30, micro a processor 36, an analog input-output device 37, a discrete input-output device 38, a driver for communication with ACS 39 and a driver for communication with a PC 40.

Combined security system works as follows:

1. Description of the general principle

The signals from the primary current transformers 11 and voltage 12 of the protected object are fed through resistors R to the intermediate transformers T of the galvanic isolation units and preliminary scaling of the input signals in the form of current 1 and voltage 2 (Figs. 4 and 6).

Intermediate transformers T provide galvanic isolation and preliminary scaling of the input signals. The primary windings of transformers provide the specified thermal stability during overloads. Precision amplifiers implemented on microcircuits 24 and 41, diodes D, resistors R, transistors V1 and V2 are used to accurately scale signals and match the impedances of intermediate transformers and an analog-to-digital converter. From the outputs of precision amplifiers, the signals are fed to the inputs of the analog filters of the frequency filter unit 4. The low-pass filters RC (Fig. 7) pass current and voltage components of a certain frequency and do not pass high-frequency harmonics, which are interference,

distorting the sine wave of current and voltage. Next, the analog signals are fed to an analog-to-digital converter (ADC) 7 to change the waveform to discrete (digital), because subsequent signal processing will be performed by digital microcircuits. The input filtered signals through the n-channels of the signal group are fed to the multiplexer 20, which makes a serial connection of the input of the ADC 21 to one of the n-channels. The entire operation of the analog-to-digital converter 21 is controlled by a microprocessor device 22, which provides digital filtering of input signals, calculation of secondary electrical parameters of the network, and also supports exchange with a microprocessor control system of output relays and alarm in accordance with protection algorithms 10 through buffer registers 23. Microprocessor system control output relays and alarm 10 in accordance with the protection algorithms obtains the values of the electrical parameters of the protected object from of a tax-to-digital converter 7 and information about the status of digital inputs from the air-conditioning device 38. Based on this information, as well as the values of program keys and settings stored in the EPROM, control commands for the output relays and signaling are generated in accordance with the protection algorithms received through the air-conditioning system 37 to control and signaling facilities. In addition to performing protection and automation functions, the central processor of the microprocessor control system for output relays and signaling, in accordance with protection algorithms, controls the mini-display and indicators 29, maintains the keypad 30, and also provides exchange with a personal computer and ACS via channels 19 and 17. More detailed information on the operation of the microprocessor control system of output relays and alarm in accordance with protection algorithms is given in [N.N. Chernobrovov, V.A.Semenov "Relay protection of energy systems" 19 98, pp. 778-783].

2. Directional protection against single-phase earth faults - НЗ50. The zero sequence voltage 3U ₀ and the current 3I ₀ through circuits 14 and 13 are supplied to the power direction switch 3, which generates a signal that determines the direction of the zero sequence power. According to this signal, when there is a signal from the comparator 5 with the support U _OP1 to the microprocessor system 10 through the element And 8, the algorithm NZ50 is executed. When executing this algorithm, it is controlled:

- the effective value of the main harmonic of the zero sequence current 3I ₀ 50, which comes from the secondary winding

standard zero sequence current transformer (circuits 13 and 15);

- the effective value of the fundamental harmonic voltage of the zero sequence 3U ₀ coming from the "open" triangle of the voltage transformer (circuit 14);

- the angle between the vectors of the fundamental harmonics 3I ₀ and 3U ₀ .

The highly sensitive high-speed directional protection performed in this way, НЗ50 kV, has the following characteristics:

- current sensitivity 3I ₀ 50 - 2 mA;

- voltage sensitivity 3U ₀ - 5 V;

- resistance to overload on voltage 3U ₀ - 350 V;

- response zone between the vectors 3I ₀ and 3U ₀ - ± 85 °;

- the ability to set the radiation pattern in the range from 0 to 360 ° with a resolution of 1 °.

- minimum response time - 40 ms.

3. Current protection of high frequencies - TZVCh

Denote the current value of the current 3I ₀ in the frequency range from 150 to 650 Hz - 3I ₀ RF (circuit 16). In this case, not only harmonics of the frequency of 50 Hz contribute to the 3I ₀ HF, but also any “free” components in the 3I ₀ spectrum for single-phase earth faults, including unstable arc faults. A comparator 6 with a support U _ОP2 of 10 V and a response time of 40 ms is used as a trigger for registering the emergency parameter 3I ₀ HF. After the comparator 6 is activated, the RFI 3I ₀ value arriving through the filter unit 4, the analog-to-digital converter 7 is recorded in the memory 33 of the microprocessor control system of the output relays and alarm in accordance with protection algorithms 10 and can be used:

- for relative measurement according to the principle [2] with the transfer of information from the current protection of all feeders to the dispatcher and relay through the ACS 17 channel;

- for selective disconnection of a damaged connection using a special time - current dependence.

In the current protection of high frequencies, the characteristic depicted in figure 2 is used.

The current 3I ₀ HF _{max of} any connection should not exceed the sum of the currents 3I ₀ HF of the remaining connections of the section. The operation of the high frequency current protection is as follows:

in all protections at the connections of the switchgear section, the same settings are set. With a single-phase earth fault, the currents of all

undamaged connections are in the area from 0 to 3I ₀ HF _max (figure 2) and the response time TZVCh on these connections is T _max . Through the damaged connection flows the total current of all undamaged connections (section from 3I ₀ HF _max to ∑3I ₀ B4 in figure 2). Protection in the damaged area will work with time from T _min to T _max . The rest of the connections will return protection.

4. Combined protection against single-phase earth faults. In the inventive device created a combined protection against single-phase earth faults. Protection implements the above algorithms NZ50 and TZVCh.

In this case, depending on the nature of the single-phase earth faults, either one or the other algorithm operates:

- in case of stable faults, including arc faults, directional protection NZ50 applies;

- with unstable arc single-phase earth faults

current protection TZVCh applies.

The start of this or that protection is carried out according to the result of spectral analysis of the current 3I ₀ in the initial stage of a single-phase earth fault. The sign of stability / instability of the circuit - K _with .

K _s = 3I ₀ / 3I ₀ HF

where K _c is the sinusoidal coefficient of the current 3I ₀ .

The value of K _c approaches zero for short-term breakdowns and intermittent arc single-phase earth faults, and tends to ∞ for stable metal faults.

Practically for the use of K _with , the value of K _s from 0.2 to 1.0 is used as a condition for choosing protection, which is set in the form of the setting of K _cp

When K _s > K _s.p. directional protection is activated, which controls the direction of the zero sequence power - NC50.

At K _s <K _s.p. protection NZ50 is blocked and protection TZVCh is effective. Both algorithms can act both on shutdown and on alarm.

Thus, this combined relay protection device uses proven principles. The implementation of the device allowed to strengthen the advantages of each of them and reduce the disadvantages. Each algorithm has its own output relay and can be used independently for tripping and / or signaling.

Claims (1)

A combined device for relay protection against single-phase earth faults, containing galvanic isolation blocks and preliminary scaling of input signals in the form of current and voltage, a frequency filter unit, an analog-to-digital converter and a microprocessor-based control system for output relays and signaling in accordance with protection algorithms, and there are groups of outputs blocks of galvanic isolation and preliminary scaling of input signals in the form of current and voltage are connected, respectively, with the first and second the group of inputs of the frequency filter unit, the group of outputs of which is connected to the group of inputs of an analog-to-digital converter, the group of inputs and outputs of which is connected to the first group of inputs and outputs of the microprocessor-based system for controlling output relays and signaling in accordance with protection algorithms, characterized in that it contains a relay power directions, two comparators, and two AND elements, and the microprocessor-based control system for output relays and alarm in accordance with protection algorithms contains a set of bus formatters, central processor, supervisor, two random access memory devices, read-only memory, clock, two sets of buffer registers, mini-display and indicators, keyboard, microprocessor, analogue input-output device, discrete input-output device, driver for communication with ACS and a driver for communication with a PC, and the groups of inputs of the galvanic isolation blocks and preliminary scaling of the input signals in the form of current and voltage are, respectively, the first and second groups of inputs of devices the first, second and third group of inputs and outputs of which is, respectively, the second, third and fourth group of inputs and outputs of the microprocessor control system of the output relays and alarm in accordance with protection algorithms, the first input of which is connected to the output of the first element And, the first input which is connected to the output of the power direction switch, the first and second inputs of which are outputs from the output groups of the galvanic isolation units and preliminary scaling of the input signals in the form of current and voltage respectively, the second input of the first element And is connected to the output of the first comparator, the first input of which is connected to the first output from the group of outputs of the frequency filter unit, the second output from the group of outputs of which is connected to the first input of the second comparator and the first input of the second element And, the second the input of which is connected to the output of the second comparator, the output of the second element And is connected to the second input of the microprocessor control system of the output relays and alarm in accordance with protection algorithms, the second inputs of the first of the second and second comparators are connected to the circuits of the first and second reference voltages, respectively.