JP2001095143A - Current differential protective relay apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the overcompensation by the charging current compensation circuit of a current differential protective relay apparatus. SOLUTION: When a current differential calculation unit 6a confirms that a self-end breaker 2a is in a closed state by a signal S2a and also that a self-end current S3a is larger than 0, only if an output 10a which starts a charging current compensation circuit exists, practices the charging current compensation calculation by using a self-end voltage S7a and a charging current set value 11a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current differential protection relay for detecting an abnormality in a power system and protecting the system.

[0002]

2. Description of the Related Art In a current-operated protection relay device installed for the purpose of system protection, a device installed in a cable system always uses a charging current compensation circuit.

[0003] As an example of this, a charging current compensation method based on idle end detection disclosed in Japanese Patent Application Laid-Open No.
-200945 discloses a charging current method in consideration of voltage fluctuation.

However, since the charging current compensating circuit differs in the magnitude of the charging current depending on the installation system, it is necessary to set the compensation of the charging current calculated by the cable length and the wire type for each installation system. Further, it is generally known that the magnitude of the charging current depends on the fluctuation of the voltage of the system. For this reason, the fluctuation of the system voltage is corrected for the charging current value set for each system as shown in equation (1), and the charging current value at the time of occurrence of a system fault can be obtained. By removing the obtained charging current value from the current at the own end and calculating the difference from the current at the other end, it is possible to make an accurate accident judgment.

[0005] The compensation equation is an a-phase equation as a representative phase.

[0006]

(Equation 1)

[0007]

In the above prior art,
By performing the charging current compensation, it is possible to compensate for a change in the charging current due to the voltage fluctuation according to the system state. But,
Performing the charging current compensation even when the self-end circuit breaker is in the “open” state and the self-end current is zero is overcompensated by the set value of the charging current because the voltage that can be taken in is the bus voltage. Further, when the self-end circuit breaker is turned on, in the transient period immediately after the turning on, the system voltage fluctuates and the timing of overcompensation similarly occurs due to the time difference until the current is actually detected. In this case, a difference current is generated depending on the set value of the charging current and the amount of voltage fluctuation, and the current differential protection relay device becomes unnecessary. In order to avoid this, in order to prevent a malfunction (unnecessary response) due to the charging current generated in the system, it is necessary to restrict the relay sensitivity.

It is an object of the present invention to provide a charging current compensating circuit which overcomes the problems of the prior art and promotes system status.

[0009]

The self-end breaker is in the "on" state, and the self-end current is flowing (Ia> 0) by using the breaker information and current information taken into the self-end. By using the charging current compensating circuit under the condition, overcompensation in system operation or the like can be prevented, and charging current compensation according to the system state can be performed.

[0010] The current differential protection relay is installed for the purpose of detecting and shutting off a system fault at high speed and surely, but there has been a problem that the relay sensitivity is conventionally restricted by the influence of the charging current. According to this patent, after the breaker is turned on and the current is checked, the operation of the protection relay is permitted, so that unnecessary operation due to a transient state before or immediately after the breaker is turned on can be prevented, and high sensitivity and high speed operation characteristics Can be provided.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIGS.
This will be described in detail in Section 2.

FIG. 1 shows the configuration of a current differential protection relay device according to this embodiment.

In order to protect the transmission line 1 connecting the electric stations A and B via the circuit breakers 2a and 2b, the electric stations A and B
B are provided with current differential protection relays 4a and 4b, respectively.

The current differential protection relay 4a at the substation A is
The current S3a detected via the current transformer 3a and the current S3b of the current transformer 3b sent via the transmission line 5 from the current differential protection relay 4b at the substation B were converted into digital signals. Thereafter, the current differential operation unit 6a determines a failure.

Here, when the transmission line 1 is a cable system, when the circuit breakers 2a and 2b are turned on, a charging current 1c flows due to the floating capacitance C between the cable and the ground. At this time, a current S3a corresponding to the charging current 1c is taken into the current differential protection relay 4a via the current transformer 3a. A calculation example of the current differential calculator 6a at this time is shown below.

Normally, the system current 2 from the substation A to the substation B is
When i flows, the current differential calculator 6a calculates the differential between the current S3a from the current transformer 3a and the current S3b from the current transformer 3b as S3a-S3b, and since S3a = S3b, the differential operation is performed. Operation = 0. However, considering the cable system,
Since the differential operation unit 6a becomes S3a obtained by adding the charging current Ic to the system current 2i, the differential operation becomes Ic, and the charging current 1c is calculated as a difference.

In the conventional method, the charging current is compensated by apparently setting the differential operation to 0 by adding this difference as a correction value to the calculation unit in advance.

The operation equation is shown in equation (2).

[0019]

## EQU2 ## Differential operation = | (S3a-11a) -S3b | ..... (2) S3a: current (2i + Ic) to which charging current is added S3b: system current (2i) 11a: charging current Set value (corresponding to Ic) Further, as described in the previous section, the charging current Ic responds to a change due to the voltage fluctuation of the electric station A. The fluctuation of the charging current Ic due to the system fluctuation is caused by the charging current set value 1 being a fixed value.
1a alone does not provide sufficient compensation. The bus voltage S7a detected via the transformer 7a at the local terminal substation A captures the transient voltage change value and combines it with the charging current set value 11a to obtain the correction value 8a. A correction circuit is provided.

However, this condition is valid for a complete one-line ground fault during normal operation when both the circuit breakers 2a and 2b are closed.
When both the circuit breakers 2a and 2b are open, the charging current 1c
Even when is zero, the correction value is always superimposed on the calculation unit, resulting in overcompensation.

When this is expressed by the equation (2), the condition is that the circuit breakers 2a and 2b are in an open state with respect to the equation (2), so that both the load current 2i and the charging current 1C flowing through the transmission line 1 are 0.

And a current S3 flowing through the current differential operation unit 6a.
a and S3b are also 0.

The result of the differential operation at this time is

[0024]

(Equation 3) And the charging current set value 11a is calculated as the difference,
The relay sensitivity needs to be set higher than this value. As a remedy, over-compensation of the charging current correction value 8a when the breakers 2a and 2b are open is confirmed by confirming the "on" state signal S2a of the breaker 2a at its own end in the starting condition 10a of the charging current compensation. It is possible to avoid.

FIG. 2 shows a current differential protection relay operation unit 6a.
FIG.

When the system current 2i at the moment when the self-interrupting circuit breaker 2a is turned on and the current input of the current differential operation unit are represented in time series, the detection of the current input of the current differential operation unit is a detection delay time τ. Occurs. This is due to the delay of the filter for A / D conversion and removal of harmonics and noise.

At this time, the charging current correction value is
a In the “off” state, the unnecessary correction value 21 is overcompensated,
This case can be improved as described above. But,
Immediately after the self-end breaker 2a is turned on, an excessive voltage correction is added to the charging current set value under the influence of the transient voltage fluctuation, and the unnecessary correction value 22 is overcompensated.

As a result, dt from the time immediately after the self-end breaker 2a is turned on to the time when the current input is actually detected by the current differential calculator is obtained.
Since it remains as time and overcompensation, if it is left as it is, there is a restriction such as a decrease in relay sensitivity. As a remedy for this, the presence / absence of the self-end current S3a taken into the current differential calculation unit 4a is determined by a startup determination circuit, and the charging current compensation startup condition 10a
By performing the charging current compensation at, it is possible to avoid a decrease in the relay sensitivity.

[0029]

According to the present invention, an over-compensation in the case where no charging current is generated is avoided by adding a self-end circuit breaker "on" and a self-end current "present" condition to the starting condition of the charging current compensation circuit. Therefore, the sensitivity of the current differential protection relay is not restricted, and the sensitivity can be increased and the reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a current differential protection relay device according to an embodiment of the present invention.

FIG. 2 is a time chart illustrating the operation of the current differential protection relay device according to the present invention.

[Explanation of symbols]

1… Transmission line, 2a ・ 2b… Circuit breaker, 3a ・ 3b… Current transformer, S2a ・ S2
b: Circuit breaker status judgment, S3a / S3b: System current, 4a / 4b: Current differential protection relay, 5: Transmission line, 6a / 6b: Current differential operation unit, 7a / 7b: Transformer, S7a / S7b… Bus voltage, 8a ・ 8b…
Correction value, 9a / 9b ... Charging current compensation start determination circuit, 10a / 10b
… Charge current compensation start condition, 11a ・ 11b… Charge current set value,
21: Overcompensation when circuit breaker is turned off, 22: Overcompensation immediately after circuit breaker is turned on.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hitoshi Oku 3-2-1 Sachimachi, Hitachi City, Ibaraki Prefecture Within Hitachi Engineering Co., Ltd. (72) Inventor Kazuaki Kumagai 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture No. 1 Hitachi Kokubu Office Hitachi, Ltd. (72) Inventor Shinji Komatsu 1-1-1, Kokubuncho, Hitachi City, Hitachi, Ibaraki F-term (reference) 5G047 AA01 AB01 BA01 BB03 CA03 CB02

Claims (1)

[Claims] 1. A voltage of a transmission line installed between buses is measured, a charging current between lines of the transmission line and a charging current to the ground are determined based on the voltages, and the charging current is subtracted from the current of the transmission line. A current having a charging current compensation function of detecting an abnormal current flowing through the transmission line by a differential operation based on the current value obtained, and opening circuit breakers at both ends of the transmission line to cut off the transmission line from the bus. Conventionally, in a protective relay using a differential transmission line protection method, an abnormal current may be detected and operated unnecessarily due to the influence of the charging current compensation function depending on the state of the system, and the application means is complicated. A current differential protection relay device comprising means for controlling charging current compensation based on a breaker "on" condition and a current "present" condition at each protection relay device installation end. .