CN113036734B - Traction network power supply arm relay protection method based on directional current increment element - Google Patents

Abstract

The invention discloses a traction network power supply arm relay protection method based on a directional current increment element. The pavilion of the traction network is connected to a power supply arm through a circuit breaker, and the circuit breaker is provided with a feeder line protection device; the feeder line protection device comprises a directional current increment element and also forms a protection unit; after the directional current increment element is started, tripping off a circuit breaker corresponding to the feeder line protection device and sending a joint tripping signal or a locking signal to the feeder line protection devices of the same group of protection units; the feeder line protection device trips off a corresponding circuit breaker after receiving the joint tripping signal, and locks and protects after receiving a locking signal; and setting the starting condition of the directional current increment element according to the full length of the power supply arm. The invention has the advantages that the full length of the power supply arm can be independently protected; the deficiency of the protection range is made up through the jump signal, and the deficiency of the selectivity is made up through the locking signal, so that the integral protection of the power supply arm is formed; the fault power supply arm can be quickly isolated after the fault, and the power supply of the non-fault side power supply arm is not interrupted.

Description

A Relay Protection Method for Power Supply Arm of Traction Network Based on Directional Current Incremental Element

technical field

The invention relates to the technical field of electrified railway power supply, in particular to a method for relay protection of a power supply arm of a traction network based on a directional current incremental element.

Background technique

High-speed railway EMUs have the characteristics of high operating speed, large traction power, and short departure intervals. The high-speed railways in many countries adopt the fully parallel AT power supply method, and the uplink and downlink wires of the same name are connected in parallel in the substation, AT station and divisional station. This power supply method can reduce the unit impedance of the traction network, improve the network voltage of the traction network, and increase Power supply capability, reduce electromagnetic interference and other advantages. However, when a fault occurs on the line, it has the characteristics of large fault current, many fault circuits, and complex fault current distribution. Relay protection must cut off all fault circuits in substations, AT stations, and partition stations to isolate the fault section. Protection exists The conflict between quickness and selectivity.

At present, when a fault occurs in the high-speed railway traction network, the current relay protection method first trips the substation to protect the uplink and downlink circuit breakers, and then realizes parallel disconnection and fault isolation according to the loss of voltage criterion and reclosing. This protection method cannot distinguish the faulty power supply arm. When isolating the fault, both the uplink and downlink power supply arms must be powered off first, and then rely on reclosing to make up for the lack of protection selectivity. It takes a long time to restore power supply and expands the scope of power outages.

Patent CN 103715670 A "A High-Speed Railway Power Supply Arm Joint Jump Protection Method Based on Impedance Characteristics" configures impedance protection with quadrilateral action characteristics in substations, AT stations, and partition stations, and forms a whole for the power supply arm through the joint jump signal Protect. Patent CN 103715671 A "A High-speed Railway Power Supply Arm Joint Commissioning and Protection Method Based on Current Characteristics" configures the current ratio criterion and overcurrent criterion in the substation, and configures the direction overcurrent criterion in the AT station and the partition station, and passes The joint jump signal constitutes the overall protection of the power supply arm. Both of the above two schemes jointly protect the power supply section between the substation and the AT station through the protection of the substation and the AT station, and jointly protect the power supply section between the AT station and the partition station through the protection of the AT station and the partition station. Each protection device cannot protect the entire power supply arm alone, and once the communication fails, the protection will refuse to operate.

Contents of the invention

The invention discloses a relay protection method for a power supply arm of a traction network based on a directional current incremental element, which can quickly isolate the faulty power supply arm after a fault, without interrupting the power supply of the non-fault side power supply arm, taking into account the selectivity and quick action of protection sex.

One circuit breaker (single-line power supply arm) or two circuit breakers (multi-line power supply arm) are installed in the non-power supply kiosk. The technical scheme of the protection method is as follows:

A method for relay protection of a power supply arm of a traction network based on a directional current incremental element, wherein the traction network includes more than two booths, each booth is connected to the power supply arm through a circuit breaker, and each circuit breaker is equipped with a feeder protection device; The feeder protection device configured with the circuit breaker on the power supply side includes a forward current incremental element, and the feeder protection device configured with a circuit breaker on the non-power supply side includes a forward current incremental element and a reverse current incremental element; The kiosk points to the power supply arm, and the reverse is that the power supply arm points to the kiosk; all feeder protection devices connected to the circuit breaker configuration of the same power supply arm constitute a group of protection units; after the forward current incremental element of any feeder protection device is activated, and in If the blocking signal sent by the feeder protection device of the same group of protection units is not received within the delay t, the circuit breaker corresponding to the feeder protection device will be tripped, and a joint trip signal will be sent to the feeder protection device of the same group of protection units; any feeder protection After the reverse current incremental element of the device is started, it sends a blocking signal to the feeder protection device of the same group of protection units; any feeder protection device jumps off the circuit breaker corresponding to the feeder protection device after receiving the tripping signal; any feeder protection device After the protection device receives the blocking signal, it blocks for protection; the forward current incremental element starts or the reverse current incremental element starts, and the starting conditions are set according to the full length of the power supply arm.

Further, the power supply arm includes an uplink power supply arm and a downlink power supply arm.

Only one circuit breaker is set on the parallel line of the non-power supply booth, and the technical scheme of the protection method is as follows:

A method for relay protection of a power supply arm of a traction network based on a directional current incremental element, wherein the traction network includes more than two booths, and the power supply booths are respectively connected to the uplink power supply arm and the downlink power supply arm through an uplink circuit breaker and a downlink circuit breaker , a parallel line circuit breaker is set on the parallel line of the non-power supply booth, and each circuit breaker is equipped with a feeder protection device; the feeder protection device of the uplink circuit breaker and the downlink circuit breaker includes a forward current incremental element pointing to the power supply arm of the booth, The feeder protection device of the parallel line circuit breaker includes a forward current incremental element pointing to the upstream power supply arm and a reverse current incremental element pointing to the downstream power supply arm; the upstream circuit breaker and the feeder protection devices of all parallel line circuit breakers constitute an upstream protection unit , the downlink circuit breaker and the feeder protection devices of all parallel line circuit breakers constitute a downlink protection unit; after the forward current incremental element of the feeder protection device of the uplink circuit breaker is started, and the feeder of the uplink protection unit is not received within the delay t The blocking signal sent by the protection device will trip the circuit breaker corresponding to the feeder protection device, and send a joint trip signal to the feeder protection device of the upstream protection unit; after the forward current incremental element of the feeder protection device of the downstream circuit breaker is activated, and If the blocking signal sent by the feeder protection device of the downlink protection unit is not received within the delay t, the circuit breaker corresponding to the feeder protection device will be tripped, and a joint jump signal will be sent to the feeder protection device of the downlink protection unit; any parallel line will be disconnected After the positive current incremental element of the feeder protection device of the feeder is started, it sends a blocking signal to the feeder protection device of the downstream circuit breaker; after a delay of t', the corresponding circuit breaker of the feeder protection device is tripped, and the feeder protection device of the upstream protection unit The device sends a joint jump signal; after the reverse current incremental element of the feeder protection device of any parallel circuit breaker is activated, it sends a blocking signal to the feeder protection device of the upstream circuit breaker; after a delay of t', the corresponding feeder protection device is tripped. circuit breaker, and send a tripping signal to the feeder protection device of the downstream protection unit; after any feeder protection device receives the tripping signal, it trips the circuit breaker corresponding to the feeder protection device; after any feeder protection device receives the blocking signal, Blocking protection: the forward current incremental element starts or the reverse current incremental element starts, and the starting conditions are set according to the entire length of the power supply arm.

The beneficial effect of the present invention is that,

(1) The feeder protection devices in each pavilion are equipped with directional current incremental elements, and each protection is set according to the full length of the protection power supply arm, which can protect the entire length of the power supply arm independently.

(2) The feeder protection devices of the same power supply arm are connected, and the lack of protection range is compensated by the joint jump signal, and the lack of selectivity is compensated by the blocking signal, which constitutes the overall protection of the power supply arm.

(3) The faulty power supply arm can be quickly isolated after a fault, and the power supply of the non-fault side power supply arm is not interrupted, taking into account the selectivity and quickness of protection.

Description of drawings

Figure 1 Schematic diagram of fully parallel AT power supply with double circuit breakers.

Figure 2 Schematic diagram of the action characteristics of the directional current increment element.

Fig. 3 Action logic diagram of double circuit breaker mode protection 1.

Fig. 4 Action logic diagram of double circuit breaker mode protection 2.

Fig. 5 Action logic diagram of double circuit breaker mode protection 3.

Fig. 6 Action logic diagram of double circuit breaker mode protection 4.

Fig. 7 Action logic diagram of double circuit breaker mode protection 5.

Fig. 8 Action logic diagram of double circuit breaker mode protection 6.

Figure 9 is a schematic diagram of a single circuit breaker full parallel AT power supply.

Fig. 10 Action logic diagram of single circuit breaker mode protection 1.

Figure 11 Action logic diagram of single circuit breaker mode protection 2.

Fig. 12 Action logic diagram of single circuit breaker mode protection 3.

Fig. 13 Action logic diagram of single circuit breaker mode protection 4.

Figure 14 Schematic diagram of normal power supply in double circuit breaker mode.

Figure 15 Schematic diagram of cross-regional power supply in double circuit breaker mode.

Figure 16 Schematic diagram of normal power supply in single circuit breaker mode.

Fig. 17 Schematic diagram of cross-area power supply in single circuit breaker mode.

Figure 18 Schematic diagram of normal power supply for double-line direct supply.

Figure 19 Schematic diagram of double-track direct power supply for cross-area power supply.

Fig. 20 is a schematic diagram of supplying power via a multi-level switching station. Among them, (a) is a single incoming line mode, and (b) is a double incoming line mode.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

(1) Protection method of double circuit breaker mode

The double circuit breaker fully parallel AT traction network has two parallel power supply lines, called the uplink power supply arm and the downlink power supply arm. The wires of the two power supply arms are connected in parallel at the substation, AT station, and partition. circuit breaker, as shown in Figure 1. 1QF~6QF in the figure are the circuit breakers installed in the substation, AT station and partition station respectively, and they are tripped by the corresponding feeder protection devices 1~6 (hereinafter referred to as feeder protection or protection 1~6).

The relay protection method of traction grid power supply arm based on directional current incremental element is as follows:

When the traction network fails, the protection 3 and 4 will flow the fault current with the same size and opposite direction, which is the change of the current before and after the fault, that is, the current increment. Similarly, the current increments at protection 5 and 6 also meet this rule. That is to say, the current increment direction of the AT station and the partition station can distinguish whether the fault occurs in the uplink or downlink: if the positive direction of the current increment element in the specified direction is from the bus to the line, when the fault occurs in the power supply arm of the side, the AT station and the The forward current incremental element of the partition will start, otherwise, the reverse current incremental element will start.

The feeder protection on the power supply side is equipped with positive current incremental elements, and the feeder protection on the non-power supply side is equipped with forward and reverse current incremental elements. The positive direction is directed from the busbar to the line, and all protections are set according to the full length of the protection power supply arm. Taking Figure 1 as an example, configure forward current incremental elements in protections 1 and 2, and configure forward and reverse current incremental elements in protections 3 to 6. Setting:

ΔI _set.S ＝K ₁ ΔI _max.S (1)

In the formula, ΔI _set.S is the setting value of the current incremental protection of each station, and the subscript S indicates the substation, AT station or partition station; K ₁ is the reliability coefficient, usually 1.2; ΔI _max.S is the normal operation of the line The maximum current change within one cycle of each booth at that time.

For the directional current incremental protection of AT stations and partition stations, the positive direction criterion is:

为灵敏角，对牵引网一般取70°；

为一周波内各所亭母线电压变化量，

为当前时刻母线电压，

一周波前母线电压；

为一周波内各保护测量电流变化量，

为当前时刻测量电流值，

为一周波前测量电流值。其方向动作特性如图2所示。In the formula,

It is the sensitive angle, which is generally taken as 70° for the traction net;

is the variation of the busbar voltage of each pavilion within one cycle,

is the current bus voltage,

Bus voltage before one cycle of wave;

Measure the current variation for each protection within a cycle,

Measure the current value for the current moment,

The current value is measured for a cycle front. Its directional action characteristics are shown in Figure 2.

After the positive current incremental element of any protection is started, and after a period of time without receiving the blocking signal of the protection of the same group, the corresponding circuit breaker of this protection will be tripped, and at the same time, a joint trip signal will be sent to the protection of the same group; After the joint trip signal of the same group, immediately trip the circuit breaker corresponding to this protection. After the reverse current incremental element of any protection is started, it will immediately send a blocking signal to the protection of the same group; after any protection receives the blocking signal, it will immediately block the protection. Taking protections 1-6 in Figure 1 as an example, protections 1, 3, 5 and protections 2, 4, 6 are respectively connected through a high-speed communication network to form a group of protection units, and their action logic is shown in Figures 3-8.

If the traction network is a single-line power supply arm, for example, there is only an uplink power supply arm in Figure 1, the protection logic is the same as this.

(2) Protection method of single circuit breaker mode

The single circuit breaker full parallel AT traction network has two parallel power supply lines, called the uplink power supply arm and the downlink power supply arm, the wires of the two power supply arms are connected in parallel at the substation, AT station, and partition, and there is a circuit breaker on the parallel line device, as shown in Figure 9. 1QF~4QF in the figure are the circuit breakers installed in the substation, AT station and partition station respectively, and they are controlled by the corresponding protection 1~4 to trip.

If the positive direction of the specified direction current incremental element points to the uplink, when the uplink traction network fails, the fault current flows upward from the downlink through protection 3 and 4, and the positive current increment element of protection 3 and 4 starts; when the downlink traction network When a fault occurs, the fault current flows from upstream through protection 3 and 4 to downstream, and the reverse current incremental element of protection 3 and 4 starts.

The feeder protection on the power supply side is equipped with forward current incremental elements, and the feeder protection on the non-power supply side is equipped with forward and reverse current incremental elements. Taking Figure 9 as an example, the forward current incremental elements are configured in protections 1 and 2, and the forward and reverse current incremental elements are configured in protections 3 and 4. The setting values and positive direction criteria of each protection are also in accordance with the formula (1) , (2) OK.

After the positive current incremental element of the feeder protection on the power supply side is started, and the blocking signal of the protection of the same group is not received after a period of time, the corresponding circuit breaker of this protection will be tripped, and a joint trip signal will be sent to the protection of the same group at the same time; the non-power supply side feeder After the forward or reverse current incremental element of the protection is activated, it immediately sends a blocking signal to the feeder protection on the power supply side in the opposite direction. The feeder protection on the non-power side sends a tripping signal. After any protection receives the tripping signal, it immediately trips the circuit breaker corresponding to this protection; after any protection receives the blocking signal, it immediately blocks the protection. Taking protections 1-4 in Figure 9 as an example, protections 1, 3, 4 and protections 2, 3, 4 are respectively connected through a high-speed communication network to form a group of protection units, and their action logic is shown in Figures 10-13.

Specific examples are as follows:

1. Normal power supply in double circuit breaker mode

For the normal power supply mode in double circuit breaker mode as shown in Figure 14, the protection implementation scheme is as follows:

Configure positive current incremental elements in protections 1 and 2; configure forward and reverse current incremental elements in protections 3 to 6, and the positive direction is directed from the bus to the line. Protection 1, 3, 5 and protection 2, 4, 6 respectively use high-speed communication network to form two groups of protection units. After the forward current incremental element of any protection is started, if no blocking signal is received after a delay of 20ms, the corresponding circuit breaker will be tripped and a joint trip signal will be sent to the protection of the same group; the reverse current increment of any protection After the element is activated, it sends a blocking signal to the rest of the protection in the same group. After any protection receives the joint trip signal, it immediately trips the corresponding circuit breaker; after any protection receives the blocking signal, it immediately blocks the protection.

2. Double circuit breaker mode cross-regional power supply

For the cross-regional power supply mode in double circuit breaker mode as shown in Figure 15, the substation SS2 is out of operation, and the substation SS1 supplies power across the district through the cross-district isolating switch 1QS of the district substation SP. The protection implementation scheme is as follows:

Configure positive current incremental elements in protections 1, 2, 7, and 8; configure forward and reverse current incremental elements in protections 3-6, 9, and 10, and the positive direction is directed from the bus to the line. Protections 1, 3, 5; protections 2, 4, 6; protections 7, 9; protections 8, 10 respectively use high-speed communication networks to form four sets of protection units. After the positive current incremental element of any protection is started, if no blocking signal is received after a delay of 20ms, the corresponding circuit breaker will be tripped and a joint trip signal will be sent to the same group of protections. After the reverse current incremental element of any protection is started, it sends a blocking signal to the rest of the protection in the same group. After any protection receives the joint trip signal, it immediately trips the corresponding circuit breaker; after any protection receives the blocking signal, it immediately blocks the protection.

3. Normal power supply in single circuit breaker mode

For the normal power supply mode in single circuit breaker mode as shown in Figure 16, the protection implementation scheme is as follows:

Configure forward current incremental elements on protections 1 and 2; configure forward and reverse current incremental elements on protections 3 and 4, with the positive direction pointing to the uplink power supply arm. Protection 1, 3, 4 and protection 2, 3, 4 respectively use high-speed communication network to form two sets of protection units. After the positive current incremental elements of protection 1 and 2 are started, if no blocking signal is received after a delay of 20ms, the corresponding circuit breaker will be tripped and a joint trip signal will be sent to the same group of protections. After the positive current incremental element of protection 3 starts, it immediately sends a blocking signal to protection 2, and after a delay of 20ms, trips the corresponding circuit breaker and sends a joint trip signal to protection 1 and protection 4; the reverse of protection 3 After the current incremental element is started, it immediately sends a blocking signal to protection 1, and after a delay of 20ms, trips the corresponding circuit breaker and sends a joint trip signal to protection 2 and protection 4. The action logic of protection 4 is similar to that of protection 3. After any protection receives the joint trip signal, it immediately trips the corresponding circuit breaker; after any protection receives the blocking signal, it immediately blocks the protection.

4. Power supply in single circuit breaker mode

For the single circuit breaker mode cross-regional power supply mode shown in Figure 17, the substation SS2 is out of operation, and the substation SS1 provides cross-regional power supply through the cross-region isolating switches 1QS and 2QS of the sub-regional substation SP. The protection implementation scheme is as follows:

Configure forward current incremental elements on protections 1 and 2; configure forward and reverse current incremental elements on protections 3 to 6, with the forward direction pointing to the uplink power supply arm. After the positive current incremental elements of protection 1 and 2 are started, if no blocking signal is received after a delay of 20ms, the corresponding circuit breaker will be tripped and a joint trip signal will be sent to the same group of protections. After the positive current incremental element of protection 3 starts, it immediately sends a blocking signal to protection 2, and after a delay of 20ms, trips the corresponding circuit breaker and sends a joint trip signal to protection 1 and protections 4 to 6; protection 3 After the reverse current incremental element is started, it immediately sends a blocking signal to protection 1, and after a delay of 20ms, trips the corresponding circuit breaker and sends a joint trip signal to protection 2 and protections 4-6. The action logic of protection 4~6 is similar to that of protection 3. After any protection receives the joint trip signal, it immediately trips the corresponding circuit breaker; after any protection receives the blocking signal, it immediately blocks the protection.

5. Double line direct supply for normal power supply

For the normal power supply in the double-line direct power supply mode shown in Figure 18, the protection implementation scheme is as follows:

Configure forward current increment elements on protections 1 and 2; configure forward and reverse current increment elements on protection 3, with the positive direction pointing to the uplink power supply arm. Protection 1, 3 and protection 2, 3 respectively use high-speed communication network to form two groups of protection units. After the positive current incremental elements of protection 1 and 2 are started, if no blocking signal is received after a delay of 20ms, the corresponding circuit breaker will be tripped and a joint trip signal will be sent to the same group of protections. After the positive current incremental element of protection 3 starts, it immediately sends a blocking signal to protection 2, and after a delay of 20ms, trips the corresponding circuit breaker and sends a joint trip signal to protection 1; the reverse current increment of protection 3 After the element is started, it immediately sends a blocking signal to protection 1, and after a delay of 20ms, trips the corresponding circuit breaker and sends a joint trip signal to protection 2. After any protection receives the joint trip signal, it immediately trips the corresponding circuit breaker; after any protection receives the blocking signal, it immediately blocks the protection.

6. Double-line direct power supply for cross-regional power supply

For the single-breaker power supply mode shown in Figure 19, the substation SS2 is out of operation, and the substation SS1 supplies power through the cross-area isolating switches 1QS and 2QS of the sub-area SP. The protection implementation scheme is as follows:

Configure forward current incremental elements on protections 1 and 2; configure forward and reverse current incremental elements on protections 3 and 4, with the positive direction pointing to the uplink power supply arm. Protection 1, 3, 4 and protection 2, 3, 4 respectively use high-speed communication network to form two sets of protection units. After the positive current incremental elements of protection 1 and 2 are started, if no blocking signal is received after a delay of 20ms, the corresponding circuit breaker will be tripped and a joint trip signal will be sent to the same group of protections. After the positive current incremental element of protection 3 starts, it immediately sends a blocking signal to protection 2, and after a delay of 20ms, trips the corresponding circuit breaker and sends a joint trip signal to protection 1 and protection 4; the reverse of protection 3 After the current incremental element is started, it immediately sends a blocking signal to protection 1, and after a delay of 20ms, trips the corresponding circuit breaker and sends a joint trip signal to protection 2 and protection 4. The action logic of protection 4 is similar to that of protection 3. After any protection receives the joint trip signal, it immediately trips the corresponding circuit breaker; after any protection receives the blocking signal, it immediately blocks the protection.

7. Power supply via multi-stage switching station

As shown in Figure 20, the power supplied by the multi-level switching station, the substation SS1 is powered by the multi-level switching station SSP1, SSP2, etc., the protection implementation scheme is as follows:

Configure positive current incremental elements in protections 1, 2, 5, and 6; configure forward and reverse current incremental elements in protections 3, 4, 7, and 8, and the positive direction is directed from the bus to the line. Protections 1 and 3, protections 2 and 4, protections 5 and 7, and protections 6 and 8 respectively use high-speed communication networks to form four groups of protection units. After the positive current incremental element of any protection is started, if no blocking signal is received after a delay of 20ms, the corresponding circuit breaker will be tripped and a joint trip signal will be sent to the same group of protections. After the reverse current incremental element of any protection is started, it sends a blocking signal to the rest of the protection in the same group. After any protection receives the joint trip signal, it immediately trips the corresponding circuit breaker; after any protection receives the blocking signal, it immediately blocks the protection. This solution is applicable to both single-entry mode and double-entry mode, as shown in Figure 20(a) and Figure 20(b).

Claims (3)

1. A kind of relay protection method of power supply arm of traction network based on directional current increment element, it is characterized in that, The traction network includes more than two booths, each booth is connected to the power supply arm through a circuit breaker, and each circuit breaker is equipped with a feeder protection device; The feeder protection device configured with the circuit breaker on the power supply side is equipped with a forward current incremental element, and the feeder protection device configured with a circuit breaker on the non-power supply side is configured with a forward current incremental element and a reverse current incremental element; The kiosk points to the power supply arm, and the reverse is that the power supply arm points to the kiosk; All feeder protection devices connected to the circuit breaker configuration of the same power supply arm form a group of protection units; After the positive current incremental element of any feeder protection device is started, and the blocking signal sent by the feeder protection device of the same group of protection units is not received within the delay t, the circuit breaker corresponding to the feeder protection device is tripped and sent to The feeder protection devices of the same group of protection units send a joint jump signal; After the reverse current incremental element of any feeder protection device is activated, it sends a blocking signal to the feeder protection device of the same group of protection units; After any feeder protection device receives the tripping signal, it trips the circuit breaker corresponding to the feeder protection device; After any feeder protection device receives the blocking signal, it will block for protection; The forward current incremental element starts or the reverse current incremental element starts, and the starting conditions are set according to the entire length of the protection power supply arm. 2 . The method for relay protection of traction network power supply arm based on directional current incremental element according to claim 1 , wherein the power supply arm includes an uplink power supply arm and a downlink power supply arm. 3 . 3. A relay protection method for the power supply arm of the traction network based on the directional current incremental element, characterized in that the traction network comprises more than two booths, and the power supply booths are respectively connected to the upstream circuit breaker and the downstream circuit breaker. For the power supply arm and the downlink power supply arm, a parallel line circuit breaker is installed on the parallel line of the non-power supply booth, and each circuit breaker is equipped with a feeder protection device; The feeder protection devices of the upstream circuit breaker and the downstream circuit breaker are configured with forward current incremental elements pointing to the power supply arm, and the feeder protection devices of the parallel line circuit breaker are configured with forward current incremental elements pointing to the upstream power supply arm and pointing to the downstream power supply arm The reverse current increment element; The upstream circuit breaker and the feeder protection devices of all parallel circuit breakers constitute the upstream protection unit, and the downstream circuit breaker and the feeder protection devices of all parallel circuit breakers constitute the downstream protection unit; After the positive current incremental element of the feeder protection device of the upstream circuit breaker is started, and the blocking signal sent by the feeder protection device of the upstream protection unit is not received within the delay t, the corresponding circuit breaker of the feeder protection device is tripped, and Send a tripping signal to the feeder protection device of the upstream protection unit; After the forward current incremental element of the feeder protection device of the downlink circuit breaker is started, and the blocking signal sent by the feeder protection device of the downlink protection unit is not received within the delay t, the corresponding circuit breaker of the feeder protection device is tripped, and Send a tripping signal to the feeder protection device of the downstream protection unit; After the positive current incremental element of the feeder protection device of any parallel circuit breaker is started, it sends a blocking signal to the feeder protection device of the downstream circuit breaker; after a delay of t', the corresponding circuit breaker of the feeder protection device is tripped, and the upstream The feeder protection device of the protection unit sends a joint jump signal; After the reverse current incremental element of the feeder protection device of any parallel circuit breaker is started, it sends a blocking signal to the feeder protection device of the upstream circuit breaker; after a delay of t', the corresponding circuit breaker of the feeder protection device is tripped, and the downstream The feeder protection device of the protection unit sends a joint jump signal; After any feeder protection device receives the tripping signal, it trips the circuit breaker corresponding to the feeder protection device; After any feeder protection device receives the blocking signal, it will block for protection; The forward current incremental element starts or the reverse current incremental element starts, and the starting conditions are set according to the entire length of the protection power supply arm.

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