JP2012019588A5 - - Google Patents

Description

In order to selectively start and stop multiple circuits, circuit breakers are generally built in switchboards (metal switchgears, gas-insulated switchgears, air-insulated switchgears, etc. are collectively referred to as “switchboards”). The switchboard is provided with a protection relay such as a ground switch and a ground fault overcurrent protection relay 51G for each line. The protective relay such as the ground fault overcurrent protective relay 51G inputs the secondary output of each phase CT (current transformer) that uses each of the three-phase insulated cables for each line in the switchboard or the like as a primary conductor as an operating current. .

Therefore, the induced current flowing through the UVW three-phase insulated cable also appears in the secondary output of each phase CT (current transformer) using each of the three-phase insulated cables as a primary conductor. The secondary output is also in a three-phase unbalanced current state, and a protective relay such as the ground fault overcurrent protection relay 51G that uses the secondary output of each phase CT (current transformer) may operate (unnecessary operation or malfunction). There is.

The malfunction prevention device of the protective relay according to the present invention is provided on the load side of the protective relay connected to the common circuit of the output circuit of the input CT of each phase of the three-phase AC circuit and the input CT of each phase. A grounding switch for each phase for grounding the three-phase AC circuit by selective switching, and a common grounding line through which a combined current of a grounding circuit of the grounding switch for each phase flows. The secondary output of the input CT of each phase based on the three-phase unbalanced induced current flowing through the through hole of the primary conductor of any one of the input CTs of the phase in the opposite polarity to the primary conductor and flowing in the stop line The current is canceled by the common circuit of the output circuit of the input CT of each phase.

The present invention selects a protective relay connected to the common circuit of the output circuit of the input CT of each phase of the three-phase AC circuit, and the corresponding three-phase AC circuit provided on each load side of the input CT of each phase A grounding switch for each phase to be grounded by switching, and a common grounding line through which a combined current of a grounding circuit of the grounding switch for each phase flows, and the common grounding line is one of the input CTs for each phase. The secondary output current of the input CT of each phase based on the three-phase unbalanced induced current flowing through the through hole of the primary conductor of one input CT in the opposite polarity to the primary conductor and flowing through the stop line is the input CT of each phase . Because it is canceled by the common circuit of the output circuit, the protective relay in the stop line due to the three-phase unbalanced induced current from the operation line to the stop line in the power system or the three-phase unbalanced discharge current from the ground capacitance Prevents malfunction It is possible to prevent malfunction of the protective relay in the stop line due to the three-phase unbalanced induction current from the operation line to the stop line in the power system or the three-phase unbalanced discharge current from the ground capacitance. It is possible to easily realize a malfunction prevention device for a protective relay.

As illustrated in FIG. 1, two transmission lines L1 and L2 are connected to the substation S / S, and the transmission lines L1 and L2 transmit, for example, at 22 kV as an aerial line by the transmission tower TT.

In other words, as illustrated in FIG. 6, the three-phase phases of the receiving wire RL2 are marked as ICU, ICV, ICW, but the three-phase unbalance flowing through the power receiving cables ICU, ICV, ICW of these three-phase phases. The induced current is used as a primary current, for example, a CT (current transformer) CTU secondary output current iu with a U-phase power receiving cable ICU as a primary conductor, and a CT (current transformation) with a V-phase power receiving cable ICV as a primary conductor. The secondary output current iv of the CTV and the secondary output current iw of the CT (current transformer) CTW having the W-phase power receiving cable ICW as the primary conductor are not the same in size and direction, for example As indicated by the arrows, the secondary output current iv and the secondary output current iw and the secondary output current iu are in opposite directions, and their magnitudes do not become iu + iv + iw ≠ 0, and the difference current of iu + iv + iw is Remaining As the operating current of the ground fault overcurrent protection relay 51G connected to the circuit RCC (common circuit of the CTU, CTV and CTW (shown by the bold line in the figure)), the difference current flows and the operation of the ground fault overcurrent protection relay 51G When the value is exceeded, the ground fault overcurrent protection relay 51G operates. That is, since the ground fault overcurrent protection relay 51G operates except for the ground fault accident current, it malfunctions.
In other words, when a three-phase unbalanced induced current flows through the stop line L2 of the system corresponding to the primary conductor (power receiving cable) ICU, ICV, ICW of each phase input CT of the ground fault overcurrent protection relay 51G, the three-phase When the combined differential current of the unbalanced induced current is large, the ground fault overcurrent protection relay 51G corresponding to the stop line L2 malfunctions.

As an example of the specific means, as illustrated in FIG. 6, the ground switches ESU, ESV connected to the load side of the input CT (current transformer) CTU, CTV, CTW of the ground fault overcurrent protection relay 51G. The three-phase unbalanced induced current flowing in the grounding circuit ECU, ECV, ECW of the ESW is synthesized by, for example, the short-circuit bar SB, and the three-phase unbalanced induced current synthesized by the short-circuit bar SB is connected to the ground side of the short-circuit bar SB The common ground line CEC is configured to flow to the ground through the common ground line CEC, and the common ground line CEC is one of the input CTs (current transformers) CTU, CTV, CTW of the ground fault overcurrent protection relay 51G, for example, input CT (current transformer) CTU, the primary conductor through hole (primary conductor at a receiving line ICU through holes) (hereinafter, abbreviated as "primary conductor through holes") in the primary conductor opposite polarity so as Penetrated As a configuration.

CB11, CB12, CB21, CB22 circuit breaker,
CEC common ground line, Ce to ground capacitance,
CT current transformer, CTU U-phase input CT,
CTV V-phase input CT, CTW W-phase input CT,
DSB power receiving panel, ECU U phase grounding circuit,
ECV V phase grounding circuit, ECW W phase grounding circuit,
ES ground switch, ESU U phase ground switch,
ESV V-phase grounding switch, ESW W-phase grounding switch,
FL1, FL2 feed line,
ICU, ICV, ICW power receiving cable (three-phase AC circuit) (each phase power cable ) ,
L load, L1 three-phase AC transmission line (operation line),
L2 3-phase AC transmission line (stop line),
RCC residual circuit, RL1, RL2 receiving wire,
SB short bar, S / S substation,
Tr1, Tr2 transformer, TT power transmission tower,
u1, v2, w3, u4, v5, w6 each phase transmission line,
50,51 Overcurrent protection relay,
51G Ground fault overcurrent protection relay.

Claims (4)

The input CT of each phase of the three-phase AC circuit, the protective relay connected to the common circuit of the output circuit of the input CT of each phase, and the corresponding three-phase AC provided on each load side of the input CT of each phase A grounding switch for each phase that grounds the electric circuit by selective switching, and a common grounding line through which a combined current of the grounding circuit of the grounding switch for each phase flows, and the common grounding line of the input CT of each phase through either one of the primary conductor and the opposite polarity to the through hole of the primary conductor of the input CT, the secondary output current of the input CT of the respective phases based on the three-phase unbalanced currents flowing through the stop line of the phase A device for preventing malfunction of a protective relay that is canceled by a common circuit of an output circuit of an input CT.   2. The protective relay malfunction prevention device according to claim 1, wherein the current of the ground circuit of the ground switch of each phase is synthesized by a short-circuit bar.   In the malfunction prevention apparatus of the protective relay of Claim 1 or Claim 2, the said three-phase alternating current circuit is a three-phase receiving wire which consists of an insulated cable, The said three-phase receiving wire and input CT of each said phase, An apparatus for preventing malfunction of a protective relay, wherein the ground switch of each phase, the ground circuit of the ground switch of each phase, and the common ground line are provided on the same switchboard.   4. The protective relay malfunction prevention device according to claim 3, wherein the protective relay is provided in the switchboard.