KR980012761A - Directional overcurrent relay for transmission line protection - Google Patents

Abstract

The present invention relates to a directional overcurrent relay for quickly detecting a fault in a transmission line and eliminating an accidental line from a normal line. When the voltage disappears during operation of the circuit breaker, unless the overcurrent relay is restored, It is possible to operate without a time delay in case of a failure in the magnetic direction while giving a cycle time delay so that the disappearance of the reference vector voltage and the time delay in the direction reversal do not affect the operation of the directional overcurrent relay, The voltage storage capability is provided for the case where the voltage disappears when the voltage is turned off, and a time delay of one week is added to prevent malfunction during the direction reversal.

Description

Directional overcurrent relay for transmission line protection

FIG. 1 is a block diagram of a conventional directional overcurrent relay,

FIG. 2 shows a process of opening the circuit breaker of FIG. 1,

FIG. 3 is an operation timing diagram of FIG. 1,

FIG. 4 is a diagram illustrating a protection algorithm of the present invention and an auxiliary relay operation time;

5 is a configuration diagram of a direction overcurrent relay for protecting a transmission line according to the present invention;

6 is a timing chart of each part when a failure occurs in a line in another direction in the apparatus of the present invention

Description of the Related Art [0002]

1: Direction relay 2: Overcurrent relay

PT: Instrument transformer D: Directional element

lOC: Instant element TOC: Instant element

10: Trim holding section 20: Delay section

30: momentary tril portion 40: one-time trip portion

AND1 to AND5: end gate OR: OR4:

The present invention relates to a directional overcurrent relay for quickly detecting a fault in a transmission line and removing an accidental line from a normal line, and more particularly, to a directional overcurrent relay suitable for a directional reverse fault and a near-end fault. Generally, the line protection method by the overcurrent relay is a protection relay method operated by the fault current size. When there is power at one end of the transmission line, the direction of fault current is fixed and the operation is generally performed. The direction of the current flowing in the relay changes according to the accident point in the case of the loop transmission line or the case of the load side of the parallel two-wire transmission line, so that the overcurrent relay is made to operate only in a certain directional current . The directional relay uses a voltage as a reference vector to determine the direction of the current, and since the product of the voltage and the current becomes the operating torque, a wiring scheme that exhibits the largest polarity when a fault occurs is often used. FIG. 1 is a configuration diagram of a conventional directional overcurrent relay. As shown in FIG. 1, a transformer CT for detecting a current is installed in a transmission line, a meter transformer PT for measuring a transmission voltage, (1) for determining the voltage measured from the current transformer (PT) as a reference vector and determining the direction of the current detected from the current transformer (CT). And an overcurrent relay 2 connected to the directional electric machine 1 and operating the circuit breaker from the magnitude of the detection current transmitted from the directional relay 1. The operation of the overcurrent relay 2 is described with reference to FIGS. 2 and 3 Explain. The directional relay 1 operates only in a certain direction of the current detected through the current transformer CT in the event of an accident and uses a voltage as a reference vector to determine the direction of the current. In this case, the direction of the fault current is determined by using the past voltage or the storage voltage, and the elapsed time for the operation of the protection algorithm is determined The auxiliary relay (not shown) is operated and the breaker is operated to complete the opening of the breaker. Also, in the case of protecting the two parallel lines as shown in FIG. 1, if a rear-end accident occurs at the relay installation point, the directional relay 1 does not operate but the overcurrent relay 2 can operate. (2) is activated only when the directional relays (1) are operated, or when the directional relays (2) are activated only when the directional relays (1) are operated, or when the directional elements are operated earlier than the return of the overcurrent elements, . FIG. 3 is a timing chart of an operation process of a conventional directional overcurrent relay. When the overcurrent relay 2 starts to operate when a fault occurs at a time t1 and the fault is removed at a time t2, And the operation of the overcurrent relay 2 is stopped. In the conventional device operating in this way, the reference voltage, which is a reference vector, may be destroyed during the operation of the circuit breaker. In this case, it is necessary to determine how much of the past voltage is to be used by appropriately considering the breaker operation time. In order to appropriately process the 'lap time' in which the direction relay operates at the time point t2 of FIG. 3, it is necessary to start the overcurrent relay only when the direction relay 1 operates, In case of the former, if the over-current relay is started after the direction relay is started, it is possible to prevent the malfunction of the relay in the direction reversal. However, if the fault occurs in the line of the own section, Since the overcurrent relay operates after the relay is activated, The time delay occurs due to the determination of the direction of the line. Also, in the latter case, when the direction reversal operates properly, the operation time is delayed with respect to the failure occurring in the line of the own section. In order to solve the same problem, if the voltage disappears during the circuit breaker operation, if the overcurrent relay is not restored, the already generated trip is maintained and the one-cycle time delay is given, And the time delay when the voltage is turned off and the direction is reversed does not affect the operation of the direction overcurrent relay, which will be described in detail with reference to the accompanying drawings. FIG. 5 is a schematic diagram of a directional overcurrent relay for protecting a transmission line according to the present invention. FIG. 5 is a schematic diagram of a directional overcurrent relay for protecting a transmission line of an overcurrent relay 2, A delay unit 20 for delaying the operation of the directional element by one cycle and an output unit for combining the output of the delay unit 27 and the output of the trim holding unit 10 A second end gate AND2, and an output of the trim holding unit 17 inversely. A second end gate ANO3 for end-combining the output of the directional element D and an output of the second and third end gates AND2 and AND3 and an output of the instrument transformer PT of the first diagram An instantaneous trip section 30 which combines the output of the second gate O2 and the output of the instantaneous element 1OC and a second gate O2 that combines the second gate O2 (TOC) and an output of the time constant element (TOC). The trip maintaining unit 10 includes a first OR gate OR that combines the instantaneous component 1OC of the overcurrent relay 2 with the output of the TOC in the apparatus of FIG. 1, A first end gate (AND1) receiving the output of the OR gate (ORI) and inverting the output of the direction element, and a second end gate And a flip-flop (FF) that is input to the clock terminal (CLK) while being cleared when the output of the first end gate (ANDI) is in a low state. The instantaneous toe rim 37 includes a third OR gate OR3 receiving the output of the second OR gate OR2 and receiving a fed instantaneous trip signal lOC Trip, And a fourth end gate (AND4) for outputting an instantaneous trip call (lOC Trlp) by combining the output of the instantaneous element (OR3) and the instantaneous element (lOC) A fourth O gate 0174 which receives the output of the clock signal OR2 and receives the feedback clock signal TOC Trip and the output of the 714 gate OR4 and the output of the time element TOC, And a fifth end gate (AND5) for outputting a short-time trip signal (TOC Trip). The operation and effect of the directional overcurrent relay for protecting the transmission line according to the present invention constructed as above will be described with reference to FIGS. 4 and 7. FIG. First, to extract the protection algorithm and the auxiliary relay operation time as a basic parley, sum of the time for performing the one-period Fourier transform and the operation time of the auxiliary relay is set to a maximum of 1.5 cycles. That is, if the voltage storage capability is held at a maximum of 1.5 cycles from the current sample value until the circuit breaker is operated, then the continuous trip is maintained so long as the wave current element is not returned. If a fault occurs in the line in the magnetic direction after the setting, the direction of the current is determined based on the past voltage before 1.5 cycles. If the overcurrent element (IOC, TOC) ) And the direction element (D). The output of the high state of the directional element D is outputted from the second end gate OR2 through the third end gate AND3 to the high state to be input to the instant tripping section 30 and the short tripping section 40, In the instant trim unit 30, the output of the high state of the third gate (OR3) and the output of the high state of the instantaneous instant element (1OC) are combined by the fourth end gate (AND4), and the instantaneous trip signal Similarly, the high-state output of the second gate (OR2) in the short-time tripping unit (40) causes the fourth gate (OR4) to become a gate and the fifth gate (AND5) (TOC Trip) is outputted in the high state, so that the trip is completed. Next, a case where a failure occurs in a line in another direction will be described with reference to a sixth road. 6, if a failure occurs at the time point t1, the direction element D is not operated because a failure has occurred in the other directional line, as in the case where a failure occurs in the magnetic direction. Thus, the end gate AND of the trill holding portion 10 is activated, so that the flip-flop FF, which always receives the input of the high state at the input terminal D, is enabled, do. At this time, when the fault is removed at the time t2, the direction element D is operated due to the direction reversal, so that the delay unit 20 delays the output of the direction element D by one cycle, ). If the overcurrent element (IOC, TOC) is not turned on even after the one-cycle delay time of the delay unit 20, the high state is outputted from the delay unit 20 and the output from the second end gate (AND2) is high state Accordingly, the instantaneous trip signal lOC Trip and the short trip signal (TOC Trip) are outputted through the second gate (OR2) in the same manner as described above, whereby it is determined that a failure occurs continuously in the magnetic direction. Conversely, when the overcurrent element 1OC, TOC returns before the delay time, that is, before the delay unit 20 outputs the high state, the flip-flop The instantaneous trip signal IOC Trip and the one-time-trim signal TOCTrip are not generated as the output of the second end gate AND2 becomes low and the output of the second end gate becomes low, The apparatus of the present invention is ready to detect the failure of the magnetic-direction line again. When the power transformer PT of FIG. 1 fails, a signal at this time is input to the second OR gate OR2, thereby causing a trip to occur regardless of the directional element D. FIG. In this case, the 1-cycle time delay is the time that elapses from the use of the conversion to one-cycle fusing to extract the fundamental wave of the overcurrent element. The change of the current signal can be reflected in the effective value only when the maximum 1 cycle has elapsed. If you use the Fourier transform, you can reduce the delay time. Therefore, the maximum time delay is one cycle. As described above in detail, according to the present invention, when the voltage disappears when an accident occurs at the near end, by allowing the time lag when the voltage, which is the reference vector, and the time delay at the direction reversal do not affect the operation of the direction overcurrent relay And a time delay of one cycle is added to prevent erroneous operation at the time of direction reversal.

Claims (6)

A delay unit for delaying the operation of the directional element by one cycle, and a delay unit for delaying the output of the delay unit and the output of the trip maintaining unit when there is no output of the directional relay directional element, A third end gate for inverting the output of the trip holding part and end-combining the output of the directional element, and a third end gate for outputting the output of the second end gate and the third end gate, An instantaneous trip unit that combines the output of the second O gate and the output of the instantaneous element, and a one-time trip unit that combines the output of the second O gate and the output of the instantaneous element A directional overcurrent relay for protection of transmission lines. The directional over current relay according to claim 1, characterized in that the second O gate combines the outputs of the second and third end gates together with the output of the instrument transformer. The directional over current relay according to claim 1, wherein the delay time of the delay unit is one cycle. 4. The method according to any one of claims 1 to 3, A first end gate for receiving the output of the first gate and inverting an output of the direction element, and a second end gate for receiving the output of the direction element in a high state at all times And a flip-flop which receives the output of the first end gate to the clock terminal and is cleared when the output of the first gate is in a low state. 5. The apparatus of claim 4, wherein the instant trip device comprises: a third o gate receiving an output of the second goggle and receiving a feedback instantaneous trip signal; And a fourth end gate for outputting a trip signal. [5] The apparatus of claim 4, wherein the time trip unit comprises: a fourth o gate receiving the output of the second O gate and receiving the feedback time signal; and a fourth O gate which combines the output of the fourth O gate and the output of the time element, And a fifth end gate for outputting a signal. ※ Note: It is disclosed by the contents of the first application.