CN110676825B

CN110676825B - Circuit disconnection protection method based on voltage vector difference and backup power automatic switching and application

Info

Publication number: CN110676825B
Application number: CN201911186656.6A
Authority: CN
Inventors: 杨茹; 李静; 陈永明; 胡航; 候超; 宋丽; 曹斌; 汤大海; 魏刚; 王律; 徐溯
Original assignee: State Grid Jiangsu Electric Power Co ltd Zhenjiang Power Supply Branch
Current assignee: State Grid Jiangsu Electric Power Co ltd Zhenjiang Power Supply Branch
Priority date: 2019-11-28
Filing date: 2019-11-28
Publication date: 2021-04-27
Anticipated expiration: 2039-11-28
Also published as: CN110676825A

Abstract

The invention discloses a line disconnection protection method based on voltage vector difference and backup automatic switching and application thereof, which are characterized in that the single-phase disconnection of a 110kV line is identified by utilizing the fault characteristics of PT secondary voltages of 110kV buses of a power supply end and a load end substation when the 110kV line is single-phase disconnected and comparing the voltage vector differences of the buses at two ends of the 110kV line, the single-phase disconnection of the 110kV line is identified, a 110kV line power supply side breaker or a load side breaker is adopted, the backup automatic switching of the load end 110kV substation restores power supply, the influence of the transformer phase-lacking power supply on a power grid and the load power supply is prevented, the 110kV transformer 110kV neutral point is prevented from being burnt, and the safe and stable operation of the power grid is ensured.

Description

Circuit disconnection protection method based on voltage vector difference and backup power automatic switching and application

Technical Field

The invention relates to a line disconnection protection method based on voltage vector difference and backup power automatic switching and application, and belongs to the technical field of power equipment.

Background

At present, the phenomenon of disconnection of 110kV lines occurs in each regional power grid. The 110kV transformer powered by the 110kV line is in phase-loss operation due to line breakage, so that the three-phase voltage of the powered transformer is asymmetric, the load power supply is affected, even the 110kV neutral point of the 110kV transformer is broken down and burnt due to zero-sequence overvoltage, and the transformer is forced to be in power failure for maintenance. At present, no relay protection device specially aiming at 110kV line disconnection exists, the invention provides a single-phase disconnection relay protection method which transmits voltage information of two sides of a line through a 110kV line optical fiber channel at a load end transformer substation, compares voltage vector differences of two sides of the line to identify 110kV line disconnection, jumps a power supply side circuit breaker or a load side circuit breaker of the 110kV line disconnection line and recovers power supply through a load end 110kV transformer substation backup automatic switch.

Disclosure of Invention

The invention aims to provide a line disconnection protection method and application based on voltage vector difference and backup automatic switching, which utilize the fault characteristics of 110kV bus PT secondary voltage of a power supply end and a load end substation when a 110kV line is in single-phase disconnection, compare the voltage vector difference of buses at two ends of the 110kV line, identify the 110kV line single-phase disconnection, adopt a circuit breaker at the power supply side of the 110kV line or a circuit breaker at the load side, recover power supply by the backup automatic switching of the load end 110kV substation, prevent the influence of the phase-lacking power supply of a transformer on a power grid and the load power supply, simultaneously prevent the 110kV transformer 110kV neutral point from being burnt out, and ensure the safe and stable operation of the power grid.

The purpose of the invention is realized by the following technical scheme:

1.110kV line disconnection identification method

Method for identifying disconnection of No. 1.11 power supply incoming line circuit

Collecting secondary A-phase voltage U of 110kV bus PT3 corresponding to 220kV transformer substation at power supply end_a1Phase U of B phase voltage_b1C phase voltage U_c1 Open delta voltage 3U_o11 # 110kV line power supply side circuit breaker 4DL switching-on position information;

acquiring PT secondary of I-section bus of 110kV transformer substation at load end simultaneouslyPhase voltage U of A phase_a2Phase U of B phase voltage_b2C phase voltage U_c2Open delta voltage 3U_o21DL switching-on position information of a circuit breaker on the load side of a No. 1 110kV power supply incoming line,

conditions are as follows:

(1)|U_a1-|U_a2the voltage vector difference is larger than the vector difference setting value;

or | U_b1-U_b2The voltage vector difference of | is greater than the vector difference setting value;

or | U_c1-U_c2The voltage vector difference of | is greater than the vector difference setting value;

or |3U_o1-3U_o2The voltage vector difference of | is greater than the vector difference setting value;

(2) power end 110kV bus three-phase voltage symmetry normal of No. 1 110kV circuit, open triangle voltage 3U_oIs 0;

(3) a power end 110kV line circuit breaker 4DL of a No. 1 110kV line is at a switching-on position;

(4) a load end 110kV line breaker 1DL of a No. 1 110kV line is at a switching-on position;

when the conditions are all met, identifying and judging that the No. 1 110kV power supply line is broken, after delaying t1, performing broken line protection on 110kV in 110kV line protection of a power end 220kV transformer substation, tripping a1 # 110kV power supply line power supply side circuit breaker 4DL, performing 110kV spare power automatic switching action by a load end 110kV transformer substation, starting to trip out the 1 # 110kV power supply incoming line circuit breaker 1DL, closing a spare power supply circuit breaker 2DL or 3DL, recovering a transformer losing a power supply to the spare power supply line for power supply, and starting No. 1 110kV line broken line alarm;

or when the conditions are all met, identifying and judging that the No. 1 110kV power supply line is broken, after delaying t1, performing broken line protection on 110kV in the No. 1 110kV line protection of the load end 110kV transformer substation, jumping the No. 1 110kV power supply line load side circuit breaker 1DL, starting the closing of the standby power supply circuit breaker 2DL or 3DL by the 110kV spare power automatic switching action of the load end 110kV transformer substation, enabling the transformer losing the power supply to recover to the standby power supply line for supplying power, and starting No. 1 110kV line broken line alarm;

method for identifying disconnection of No. 1.22 power supply incoming line circuit

Collecting secondary A-phase voltage U of 110kV bus PT4 corresponding to 220kV transformer substation at power supply end_a1Phase U of B phase voltage_b1C phase voltage U_c1

Open delta voltage 3U

_o12 # 110kV line power supply side circuit breaker 4DL switching-on position information;

simultaneously collecting PT secondary A-phase voltage U of II-section bus of 110kV transformer substation at load end_a2Phase U of B phase voltage_b2C phase voltage U_c2Open delta voltage 3U_o2No. 2 110kV power incoming line load side circuit breaker 1DL switching-on position information,

conditions are as follows:

(1)|U_a1-U_a2the voltage vector difference of | is greater than the vector difference setting value;

or | U_b1-U_b2The vector difference of the electric voltage is larger than the vector difference setting value;

(2) power end 110kV bus three-phase voltage symmetry normal of No. 2 110kV line, opening triangle voltage 3U_oIs 0;

(3) a power end 110kV line circuit breaker 5DL of a No. 2 110kV line is at a switching-on position;

(4) a load end 110kV line breaker 2DL of the No. 2 110kV line is at the switching-on position;

when the conditions are all met, identifying and judging that the No. 2 110kV power supply line is broken, after delaying t1, performing broken line protection on 110kV in the protection of the 110kV line of a power supply end 220kV transformer substation, tripping a circuit breaker 4DL on the power supply side of the No. 2 110kV power supply line, performing 110kV spare power automatic switching action by a load end 110kV transformer substation, starting to trip off the No. 2 110kV power supply incoming line circuit breaker 2DL, closing a spare power supply circuit breaker 1DL or 3DL, restoring the transformer losing the power supply to the spare power supply line for supplying power, and starting No. 2 110kV line broken line alarm;

or when the conditions are all met, identifying and judging that the No. 2 110kV power supply line is broken, after a delay t1, performing disconnection protection on 110kV in the No. 2kV 110kV line protection of the load end 110kV transformer substation, tripping the No. 2kV power supply line load side circuit breaker 1DL, starting the closing of the standby power supply circuit breaker 2DL or 3DL through the 110kV spare power automatic switching action of the load end 110kV transformer substation, enabling the transformer losing the power supply to recover to the standby power supply line for supplying power, and starting No. 2kV 110kV line disconnection alarm;

1.3 when the 110kV line is broken, the tripping process is as follows:

(1) tripping off a breaker at the power supply side of the broken line;

(2) tripping off a circuit breaker on the load side of the broken line;

(3) the circuit breakers on both sides of the line break are tripped together.

The application of the line disconnection protection method based on the voltage vector difference and the backup power automatic switching comprises the following steps: the line disconnection protection method based on the voltage vector difference and the backup power automatic switching is applied to a single 110kV line disconnection protection device or a 110kV line protection device of a power end or a load end 110kV transformer substation.

The object of the invention can be further achieved by the following technical measures:

the line disconnection protection method based on the voltage vector difference and the backup power automatic switching comprises the following steps: the upper limit and the lower limit of the vector difference setting value are 4-6V.

The line disconnection protection method based on the voltage vector difference and the backup power automatic switching comprises the following steps: the t1 time is set to 0.1-0.2 seconds.

The line disconnection protection method based on the voltage vector difference and the backup power automatic switching comprises the following steps: the voltage data on both sides does not require synchronization.

The application of the line disconnection protection method based on the voltage vector difference and the backup power automatic switching is as follows: the grounding mode of a 110kV neutral point of a transformer in a load end 110kV transformer substation is as follows: ungrounded or grounded.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention fully utilizes the fault characteristics of the PT secondary voltage of the 110kV bus of the power supply end and the load end substation when the 110kV line is in single-phase disconnection, compares the voltage amplitude difference of the 110kV line two ends, identifies the 110kV line single-phase disconnection, and transfers load power supply by the load end 110kV substation through the ring closing and opening operation, thus being simple and easy.

2. According to the invention, the voltage information at two sides of the line is transmitted through the 110kV line optical fiber channel, the voltage vector difference at two sides of the line is compared to identify the line break of the 110kV line, the breaker at the power supply side or the breaker at the load side of the 110kV line is jumped, then the 110kV spare power automatic switching action of the load end transformer substation is used for starting the jumped-off incoming line breaker and closing the breaker of the spare power supply, so that the transformer without the power supply is recovered to the relay protection scheme of the power supply on the spare power supply, the influence of the phase-lacking power supply of the transformer on the power grid and the load power supply can be effectively prevented, the 110kV transformer 110kV neutral.

3. The method is implemented by adopting the 110kV line protection devices on two sides of the 110kV line, and does not need to increase hardware equipment.

Drawings

FIG. 1 is a first schematic diagram of a 110kV disconnection primary system;

fig. 2 is a first 110kV bus voltage vector diagram of 110kV line disconnection, wherein fig. 2(a) is a 110kV bus voltage vector diagram of a load side, and fig. 2(b) is a 110kV bus voltage vector diagram of a power side;

FIG. 3 is a first schematic diagram of a 110kV disconnection and load side disconnection grounding primary system;

fig. 4 is a 110kV bus voltage vector diagram of 110kV line disconnection, wherein fig. 4(a) is a 110kV bus voltage vector diagram of the load side, and fig. 4(b) is a 110kV bus voltage vector diagram of the power side;

FIG. 5 is a schematic diagram II of a 110kV disconnection primary system;

fig. 6 is a 110kV bus voltage vector diagram of 110kV line disconnection, wherein fig. 6(a) is a 110kV bus voltage vector diagram of the load side, and fig. 6(b) is a 110kV bus voltage vector diagram of the power side;

FIG. 7 is a schematic diagram II of a 110kV line break and load side line break grounding primary system;

FIG. 8 is a schematic diagram of the single-phase disconnection protection of the 110kV line of the present invention;

fig. 9 is a primary main wiring diagram of a single bus segment of a 110kV substation.

The symbols in the figures are as follows:

-representing a logical and relationship, i.e. the output is valid when all input conditions are fulfilled;

-representing a logical or relationship, i.e. the output is valid when any of the input conditions is fulfilled;

-represents the open T time relationship, i.e. the open T time when any of the input conditions is fulfilled.

Detailed Description

110kV line breakage analysis:

1.110kV line break analysis

And when the 110kV neutral point of the load side 110kV substation transformer is not grounded, the 110kV line disconnection condition is 1. And when the 110kV neutral point of the 110kV substation transformer on the load side is grounded, the 110kV line disconnection condition is 2.

1.1110 kV line broken line 1

1.1.1110 kV line broken wire

Fig. 1 is a schematic diagram of a 110kV disconnection primary system. The 110kV side of the 220kV transformer substation on the system side is an effective grounding system; 110kV neutral points of 110kV substation transformers on the load side are not grounded and are grounded through gaps.

The electric potentials of the 110kV side power supplies of the 220kV transformer substation on the system side are respectively set as E_A、E_B、E_C. When a certain part of the 110kV line is broken, such as phase A, the voltage of the 110kV bus of the 110kV transformer substation at the load side is obtained through analysis:

(1) in the formula of U_A、U_B、U_CThe voltage of A phase, B phase and C phase of 110kV bus of 110kV transformer substation at load side is U phase₀Is 110kV neutral point voltage of 110kV transformer substation on load side, 3U₀The vector diagram of the voltage of the secondary open-delta winding of the 110kV bus voltage transformer (PT for short) of the 110kV substation transformer at the load side is shown in figure 2.

When a 110kV line is broken, the voltage of the 110kV bus at the 220kV substation on the system side is E, and the voltage of the A phase, the voltage of the B phase and the voltage of the C phase are respectively E_A、E_B、E_C，3U₀Is 0, i.e. the three-phase voltage is maintained under normal conditions.

1.1.2110 kV line disconnection and load side disconnection grounding

Fig. 3 is a schematic diagram of a primary system with 110kV line break and load side line break grounded. The 110kV side of the 220kV transformer substation on the system side is an effective grounding system; 110kV neutral points of 110kV substation transformers on the load side are not grounded and are grounded through gaps.

The electric potentials of the 110kV side power supplies of the 220kV transformer substation on the system side are respectively set as E_A、E_B、E_C. When a certain part of the 110kV line is broken and the broken line of the load side is grounded, such as phase A, the voltage of the 110kV bus of the 110kV transformer substation on the load side is obtained through analysis:

(2) in the formula of U_A、U_B、U_CThe voltage of A phase, B phase and C phase of 110kV bus of 110kV transformer substation at load side is U phase₀Is 110kV neutral point voltage of 110kV transformer substation on load side, 3U₀The vector diagram of the voltage of the secondary open-delta winding of the 110kV bus voltage transformer (PT for short) of the 110kV substation transformer at the load side is shown in figure 4.

1.1.3110 kV line disconnection and system side disconnection point grounding

When the 110kV line is broken and the broken line of the system side is grounded, for the system side, the fault is mainly reflected in the single-phase grounding short-circuit fault of the 110kV line, so that the 110kV line protection of the 220kV transformer substation can start tripping to remove the fault (the 110kV line breaker trips to remove the fault, the 110kV line breaker is overlapped, then the single-phase grounding short-circuit fault of the 110kV line, the 110kV line protection of the 220kV transformer substation restarts tripping and removes the fault).

Analysis of 110kV neutral click-through of 110kV transformer substation in 1.1.4110 kV line disconnection

Table 1 shows the power frequency discharge voltage at different gaps. By analysing the neutral point to ground voltage U of the transformer₀It can be determined whether the gap is likely to break down, in conjunction with table 1.

TABLE 1 Power frequency discharge Voltage for different gaps

For the analytical results of 1.1.3, 3U₀Has a maximum value of 150V, and a neutral point to ground voltage U₀The secondary value is 50V, and the primary value is converted to obtain U₀The first value, the calculation result is as follows:

as the discharge gap of the neutral point of the transformer is 110mm or 120mm, the power frequency withstand voltage of the neutral point of the transformer shown in Table 1 is 52kV or 53.3kV, and the maximum steady-state voltage of the neutral point of the actual transformer is about 55kV and higher than the power frequency withstand voltage value, the discharge gap can be punctured.

1.2110 kV line broken line 2

1.2.1110 kV line broken wire

Fig. 5 is a schematic diagram of a 110kV primary disconnection system. The 110kV side of the 220kV transformer substation on the system side is an effective grounding system; 110kV neutral points of 110kV substation transformers on the load side are grounded.

(3) in the formula of U_A、U_B、U_CThe voltage of A phase, B phase and C phase of 110kV bus of 110kV transformer substation at load side is U phase₀Is 110kV neutral point voltage of 110kV transformer substation on load side, 3U₀The vector diagram of the voltage of the secondary open-delta winding of the 110kV bus voltage transformer (hereinafter referred to as PT) of the 110kV substation transformer at the load side is shown in FIG. 6.

1.2.2110 kV line disconnection and load side disconnection grounding

Fig. 4 is a schematic diagram of a 110kV disconnection and load side disconnection grounding primary system. The 110kV side of the 220kV transformer substation on the system side is an effective grounding system; 110kV neutral points of 110kV substation transformers on the load side are grounded.

The electric potentials of the 110kV side power supplies of the 220kV transformer substation on the system side are respectively set as E_A、E_B、E_C. When a certain broken line of the 110kV line is disconnected and the broken line of the load side is grounded, such as phase A, analyzing: e_B、E_CThe synthetic potential at the low-voltage side of the 110KV transformer substation transformer at the load side is-E_aThe potential is added to a low-voltage a-phase winding of a 110kV transformer substation at a load side and is converted into a low-voltage A-phase winding of the 110kV transformer at the winding, and the potential is-E_AGrounding the broken line of the 110kV line and the broken line of the load side to form an A-phase short circuit and an A-phase short circuit current I_AThe current of the low-voltage a-phase winding of the transformer is converted into I_aThe a-phase winding current is I_aForming a circulating current in a low-voltage side winding of the transformer, wherein the current of the a-phase winding is I_bPhase C winding current I_cFor converting the current of a high-voltage B-phase winding of a 110kV transformer into I_BC phase winding current is I_CDue to I_a、I_b、I_cThe currents are equal and in phase, so that I is_A、I_B、I_CThe currents are equal and in phase.

When the 110kV line is broken and the broken line of the transformer side is grounded, for the system side, the fault is mainly reflected in a short-circuit fault, and the zero-sequence current 31 of the system side₀＝(I_B+I_C)/3)＝2]_BAnd 3, therefore, the 110kV line protection of the 220kV transformer substation starts tripping to remove the fault (the 110kV line breaker trips to remove the fault, the 110kV line breaker is overlapped, then the 110kV line single-phase grounding short-circuit fault occurs, and the 110kV line protection of the 220kV transformer substation starts tripping again to remove the fault).

1.2.3110 kV line disconnection and system side disconnection point grounding

Analysis of 2.110 kV line breaking result

2.1110 kV line break (or and earthing at break)

For three conditions of 1.1.1, 1.1.2 and 1.2.1, 110kV line disconnection protection can be carried out, and load transfer of 110kV line disconnection can be eliminated by matching with the backup power automatic switch, so that the influence of 110kV line disconnection on power supply load can be prevented.

Short circuit caused by 2.2110 kV line disconnection and grounding at disconnection

For three conditions of 1.1.3, 1.2.2 and 1.2.3, because short-circuit fault is caused by grounding at a broken line, tripping can be started by 110kV line protection of a 220kV transformer substation to remove the fault (110kV line breaker tripping removes the fault, 110kV line breaker is overlapped, then 110kV line single-phase grounding short-circuit fault, 220kV transformer substation 110kV line protection restarts tripping again to remove the fault); because the 110kV bus corresponding to the 110kV transformer substation at the load end loses power, the load transfer of 110kV line disconnection is eliminated by the spare power automatic switching action, and the influence of the 110kV line disconnection on the power supply load is prevented.

Fault feature analysis during disconnection of 3.110kV line

For three 110kV line disconnection conditions of 1.1.1, 1.1.2 and 1.2.1, the fault characteristics are as follows: the three-phase voltage of the 110kV bus A, B, C on the power supply side is symmetrical, the amplitude and the phase are not changed greatly, and the voltage is 3U₀Is 0, but for 2 kinds of 110kV line disconnection conditions of 1.1.1 and 1.1.2, the fault characteristics are as follows: the three-phase voltage of the 110kV bus A, B, C of the load side transformer substation is asymmetrical, and the phase voltage of the broken line is-E _A2 and about 0, 3U₀is-3E_A/2 or-E_AMeanwhile, the amplitude and the phase of the non-fault phase voltage do not change much; there is a potential for breakdown of the transformer neutral. 1.2.1 the fault signature of a broken 110kV line is similar to the case of 1.1.2, where the phase voltage of the broken line is equal to 0.

In view of the above situation, the invention provides a 110kV line disconnection relay protection method for comparing voltage difference values at two sides of a line.

The power transmission and distribution network applied by the invention is a 110kV substation 110kV single-bus subsection primary main wiring (including a 110kV single-bus primary main wiring), a 110kV inner bridge wiring, a 110kV expansion inner bridge wiring, a 110kV line transformer bank wiring and other system networks. Taking a primary main connection of a 110kV single bus subsection as an example, the protection method of other primary main connections is similar. The 110kV single-bus subsection primary main wiring structure of the 110kV substation is shown in fig. 9:

the No. 1 power supply incoming line branch equipment and the No. 2 power supply incoming line branch equipment are respectively connected with a 110kV I section bus and a 110kV II section bus; a segmented circuit breaker 3DL is arranged between the first segment bus and the second segment bus of 110kV, and is connected with a segmented current transformer CT in series; the No. 1 power supply inlet line branch circuit spacing equipment is a circuit breaker 1DL and is connected with a current transformer CT1 in series; the No. 2 power supply inlet wire branch circuit spacing device is a circuit breaker 2DL and is connected with a current transformer CT2 in series; the 110kV I-section bus is also connected with a No. 1 transformer branch, a No. 2 transformer branch, a No. 1 110kV outgoing line branch and a 110kV I-section bus voltage transformer PT 1; the 110kV II-section bus is also connected with a No. 3 transformer branch, a No. 2 110kV outgoing line branch and a 110kV II-section bus voltage transformer PT 2. No. 1 power inlet wire circuit power supply side is equipped with circuit breaker 4DL, and No. 2 power inlet wire circuit power supply side is equipped with circuit breaker 5DL, and 110kV spare power automatic switching device is installed to load end 110kV electric substation 110kV side. The 110kV line is provided with an optical fiber channel and line optical fiber differential protection.

Aiming at the 110kV single-bus subsection primary main connection, a 110kV line protection device for protecting 110kV single-phase broken lines on two sides of a 110kV line is implemented, voltage information on two sides of the line is transmitted through a 110kV line optical fiber channel, voltage amplitude difference on two sides of the line is compared to identify the broken line of the 110kV line, a single-phase broken line relay protection scheme of a 110kV line power supply side circuit breaker or a load side circuit breaker is jumped, and a scheme of power supply recovery of a load end 110kV transformer substation spare power automatic switch is used for meeting field operation requirements.

The 110kV neutral point operation mode of all main transformers on the first section or the second section of buses of the load end 110kV transformer substation is as follows: a) grounding; b) not grounded, grounded through the gap. The 110kV line is provided with an optical fiber channel and line optical fiber differential protection.

The specific method of the invention is shown in figure 8:

1.110kV line disconnection identification method

simultaneously collecting PT secondary A-phase voltage U of I-section bus of 110kV transformer substation at load end_a2Phase U of B phase voltage_b2C phase voltage U_c2 Open delta voltage 3U_o2No. 1 110kV power inlet line load side circuit breaker 1DL closingThe information on the position of the mobile phone is,

conditions are as follows:

Collecting secondary A-phase voltage U of 110kV bus PT4 corresponding to 220kV transformer substation at power supply end_a1Phase BVoltage U_b1C phase voltage U_c1

Open delta voltage 3U

simultaneously collecting PT secondary A-phase voltage U of II-section bus of 110kV transformer substation at load end_a2Phase U of B phase voltage_b2C phase voltage U_c2 Open delta voltage 3U_o2No. 2 110kV power incoming line load side circuit breaker 1DL switching-on position information,

conditions are as follows:

1.3 when the 110kV line is broken, the tripping process is as follows:

(1) tripping off a breaker at the power supply side of the broken line;

(2) tripping off a circuit breaker on the load side of the broken line;

(3) the circuit breakers on both sides of the line break are tripped together.

The reason that the circuit breakers 1DL or 2DL and 4DL or 5DL on two sides of the incoming line of the 110kV power supply are arranged at the switching-on position is as follows: when a power supply incoming line is at a 110kV substation with a load end, the bus voltage far away from the power supply incoming line can also sense the line disconnection information, and the standby power supply circuit breaker for closing of the standby automatic switching can be interfered; in addition, when the line PT is adopted, the power incoming line may have other load end 110kV substations, and if the power incoming line breaker of the load end 110kV substation trips slowly or refuses to trip, the power incoming line breaker of the backup power automatic switching device may be interfered, and the backup power automatic switching device may not operate. The logic can be further optimized by adopting the condition that the 110kV power incoming line breaker is in the switching-on position.

The 110kV neutral point operation mode of the main transformer on the I section or II section of the bus of the load end 110kV transformer substation is as follows: a) grounding; b) not grounded, grounded through the gap; the 110kV side is provided with a 110kV spare power automatic switching device. No. 1 and No. 2 power supply 110kV lines are required to be provided with fiber channels and line fiber differential protection.

The method can be implemented in a single 110kV line disconnection protection device of a power supply end or a load end 110kV transformer substation or can also be implemented in a 110kV line protection device. The method is implemented in a 110kV line protection device, and has the advantage that no hardware equipment is required to be added.

The setting value of the voltage amplitude difference of the two secondary sides of the bus broken line phase PT on the two sides of the 110kV line is as follows:

(1)110kV bus PT secondary A-phase voltage value difference | U on two sides of 110kV line_a1|-|U_a2| U, B phase voltage value difference | U_b1|-|U_b2I, C phaseVoltage value difference | U_c1|-|U_c2The voltage setting value of | is as follows: setting according to the maximum unbalanced voltage greater than that in normal operation, and taking 4-6V;

(2) secondary voltage value difference |3U of PT opening triangle of 110kV bus on two sides of 110kV line_o1|-|3U_o2The voltage setting value of | is as follows: and when the voltage value is larger than the unbalanced voltage value in normal operation, taking 4-6V.

In the single-phase disconnection relay protection method for transferring load power supply by adopting ring closing and opening operation at the load end 110kV transformer substation, the setting value t1 of time is as follows: 0.1-0.2 second, and three-phase asynchronous time when the switch is closed is avoided.

The inventive solution can be used in the following cases: (1) the 110kV neutral point operation mode of all transformers of a load end 110kV transformer substation is as follows: a) grounding; b) not grounded, grounded through the gap; (2) a spare power automatic switching device is arranged on the 110kV side of the 110kV transformer substation; (3) no. 1 and No. 2 power 110kV circuit must set up fibre channel and circuit optic fibre differential protection to can satisfy following one-time main connection: (1) a 110kV single-bus subsection primary main wiring of a 110kV transformer substation; (2) a 110kV transformer substation 110kV inner bridge primary main wiring; (3) a 110kV substation 110kV primary main wiring is enlarged; (4)110kV transformer substation 110kV line group primary main wiring; (5) a primary main wiring of a 110kV line transformer bank; (6) other primary main connections.

If the 110kV transformer substation adopts primary main wiring of a 110kV line transformer set, a standby circuit breaker on the high-low voltage side of the 110kV transformer is adopted on the low-low voltage side of the load side transformer substation, and a power supply task is recovered.

For a 110kV line with branch lines, 110kV line breakage protection of pairwise correspondence between a power end transformer substation and each load end transformer substation needs to be implemented.

The scheme of the invention can also be used in the case of the disconnection of a 220kV line powered by a single power supply.

The invention adopts a method of independently arranging a 110kV line single-phase broken relay protection device in a load end substation or implementing the method in a 110kV spare power automatic switching device, and needs to add a new relay protection device or a new hardware interface; the protection device is implemented in the No. 1, No. 2 and No. 3 transformer protection devices, hardware equipment does not need to be added, and only the logic of single-phase disconnection of a 110kV line needs to be added.

The condition 1 of starting the control method for 110kV line disconnection protection by adopting the condition 2 of the control method for identifying the disconnection of each phase of the 110kV power line is not only suitable for a 110kV neutral point ungrounded mode of the transformer, but also suitable for a 110kV neutral point grounded mode of the transformer.

An example of the method of the invention is given below (taking fig. 9 as an example, the transformer 110kV neutral point operation mode is: ungrounded, grounded via a gap):

1. mode of operation 1

Under this operational mode, 2DL of No. 2 power circuit breaker, the operation of segmentation circuit breaker 3DL, 1DL of No. 1 power circuit breaker is hot standby, 1DL of No. 1 power circuit breaker branch floodgate position promptly.

No. 1.12 110kV power line single-phase line break fault

For example, if phase A is broken, phase B or phase C is broken similarly. When the phase-A single-phase disconnection fault of the No. 2 110kV power line occurs, the method is equivalent to pulling the isolating switch with load, electric arcs are generated at the disconnection moment, the electric arcs cannot be extinguished, the electric arcs further cause the phase-A single-phase grounding of the line, and the distance between the upper level No. 2kV power line and the section I or the section II of the protection range is within the distance between the upper level power line and the section I or the section II of the protection range, so that the upper level No. 2kV power line jumps away from the power side circuit breaker 5DL of the upper level No. 2kV power line through the protection; after the transformer substation at the load end loses power, the fault at the phase disconnection position of the No. 2 110kV power line A disappears, and the No. 2kV power line breaker 5DL is delayed to be successfully superposed; however, the voltage inductance of the second section of the bus of the load-side substation runs in a phase-loss mode, but the secondary voltage of the 110kV bus PT of the power supply end substation is normal, the condition that the single-phase disconnection of the No. 2 110kV power supply line is met, after the time delay t1, the 110kV line in the power supply end line protection is disconnected, and the No. 2 110kV power supply line power supply side circuit breaker 5DL is tripped. As the No. 2 110kV power line loses power, the 110kV backup power automatic switching of the 110kV transformer substation at the load end operates, the No. 2DL 110kV power circuit breaker is tripped, the No. 1DL 110kV backup power circuit breaker is started by 110kV to be switched on, and the transformer losing the power is recovered to the No. 1 backup 110kV power line to supply power.

2. Mode of operation 2

Under this operational mode, 1DL of power breaker, 3DL operation of section circuit breaker, 2 # power breaker 2DL are hot standby, 2 # power breaker 2DL separating brake position promptly.

No. 2.11 110kV power line single-phase line break fault

For example, if phase A is broken, phase B or phase C is broken similarly. When the A phase single-phase line break fault of the No. 1 110kV power line occurs, the method is equivalent to pulling an isolating switch with load, electric arcs are generated at the line break moment, the electric arcs cannot be extinguished, the electric arcs further cause the A phase single-phase grounding of the line, and the distance between the upper level No. 1 110kV power line and the I section or the II section of protection range is within the distance between the upper level power line and the II section, so that the upper level No. 1 kV power line jumps from a power side circuit breaker 4DL of the upper level No. 1 kV power line by the starting action of optical fiber differential protection; after the load end 110kV transformer substation loses power, the phase disconnection fault of the No. 1 110kV power line A disappears, and the superposition of the No. 1 110kV power line power side circuit breaker 4DL is successful after the time delay; however, the I section of the bus voltage of the load-side substation is subjected to open-phase operation, but the secondary voltage of the 110kV bus PT of the power supply end substation is normal, the condition that the 1 # 110kV power supply line is single-phase broken is met, after the time delay t1, the 110kV line in the power supply end line protection is broken, and the 1 # 110kV power supply line power supply side circuit breaker 4DL is jumped. As the No. 1 110kV power line loses power, the 110kV backup power automatic switching of the 110kV transformer substation at the load end acts, the No. 1 110kV power circuit breaker 1DL is tripped, and the No. 2kV backup power circuit breaker 2DL is started to be switched on, so that the transformer losing power is recovered to the backup No. 2kV power line for power supply.

3. Mode for operation 3

Under this operational mode, 1DL of No. 1 power circuit breaker, 2DL of No. 2 power circuit breaker operate, and the hot reserve of section circuit breaker 3DL, section circuit breaker 3DL separating brake position promptly.

No. 3.11 110kV power line single-phase line break fault

For example, if phase A is broken, phase B or phase C is broken similarly. When the A phase single-phase line break fault of the No. 1 110kV power line occurs, the method is equivalent to pulling the isolating switch with load, electric arc is generated at the line break moment, the electric arc can not be extinguished, the electric arc further causes the A phase single-phase grounding of the line, and the distance between the upper level No. 1 110kV power line and the I section or the II section of the protection range or the optical fiber differential protection starting action jumps away from the power side circuit breaker 4DL of the upper level No. 1 power line because the distance between the upper level No. 1 kV power line and the I section or the II section of the protection range is; after a first section of bus of a load end 110kV transformer substation loses power, the fault of the phase disconnection position of a No. 1 110kV power line A disappears, and the superposition of a circuit breaker 4DL on the power side of the No. 1 110kV power line is delayed to succeed; however, the I section of the bus voltage of the load-side substation is subjected to open-phase operation, but the secondary voltage of the 110kV bus PT of the power supply end substation is normal, the condition that the 1 # 110kV power supply line is single-phase broken is met, after the time delay t1, the 110kV line in the power supply end line protection is broken, and the 1 # 110kV power supply line power supply side circuit breaker 4DL is jumped. As the No. 1 110kV power line loses power, the 110kV backup power automatic switching of the 110kV transformer substation at the load end operates, the No. 1DL of the No. 1 110kV power incoming line breaker is tripped, and the 110kV backup power breaker 3DL is started to be switched on, so that the transformer losing the power is recovered to the No. 2 backup 110kV power line for power supply.

Single-phase line break fault of No. 2.22 110kV power line

For example, if phase A is broken, phase B or phase C is broken similarly. When the phase-A single-phase disconnection fault of the No. 2 110kV power line occurs, the method is equivalent to pulling the isolating switch with load, electric arcs are generated at the disconnection moment, the electric arcs cannot be extinguished, the electric arcs further cause the phase-A single-phase grounding of the line, and the distance between the phase-A single-phase grounding of the No. 2 power line at the upper level is in the protection range of the section I or the section II of the distance between the phase-A single-phase grounding and the power line at the upper level is protected by the section I or the section II of the distance between the phase-A single-phase grounding; after the II-section bus of the load-end substation loses power, the fault at the phase disconnection position of the No. 2 110kV power line A disappears, and the superposition of the No. 2 110kV power line power-side circuit breaker 5DL is successful after the time delay; however, the voltage inductance of the second section of the bus of the load-side substation runs in a phase-loss mode, but the secondary voltage of the 110kV bus PT of the power supply end substation is normal, the condition that the single-phase disconnection of the No. 2 110kV power supply line is met, after the time delay t1, the 110kV line in the power supply end line protection is disconnected, and the No. 2 110kV power supply line power supply side circuit breaker 5DL is tripped. As the No. 2 110kV power line loses power, the 110kV substation 110kV spare power automatic switching at the load end acts, the No. 2 110kV power circuit breaker 2DL is tripped, and the 110kV spare power circuit breaker 3DL is started to be switched on, so that the transformer losing the power is restored to the spare No. 1 110kV power line for power supply.

Claims

1. A line disconnection protection method based on voltage vector difference and spare power automatic switching is characterized by comprising the following steps:

method for identifying disconnection of 110kV line

1.1) No. 1 power supply incoming line breakage identification method

Collecting the switching-on position information of a secondary A-phase voltage Ua1, a secondary B-phase voltage Ub1, a secondary C-phase voltage Uc1, an open triangular voltage 3Uo1 and a No. 1 110kV line power supply side circuit breaker 4DL corresponding to a 110kV bus PT3 of a power supply end 220kV transformer substation;

meanwhile, collecting the switching-on position information of a load side circuit breaker 1DL of a load side 110kV power supply incoming line load side circuit breaker 1, wherein the load side 110kV substation I section bus PT secondary A phase voltage Ua2, B phase voltage Ub2, C phase voltage Uc2, open delta voltage 3Uo2 and No. 1 110kV power supply incoming line load side circuit breaker,

conditions are as follows:

(1) the voltage vector difference of the | Ua1-Ua2| is greater than the vector difference setting value;

or the voltage vector difference of the absolute value Ub1-Ub2 is greater than the vector difference setting value;

or the voltage vector difference of | Uc1-Uc2| is greater than the vector difference setting value;

or the voltage vector difference of |3Uo1-3Uo2| is greater than the vector difference setting value;

(2) the three-phase voltage of a 110kV bus at a power supply end of a No. 1 110kV line is symmetrical and normal, and the open triangular voltage 3Uo1 is 0;

1.2) No. 2 power supply incoming line breakage identification method

Collecting the switching-on position information of a secondary A-phase voltage Ua1, a secondary B-phase voltage Ub1, a secondary C-phase voltage Uc1, an open triangular voltage 3Uo1 and a No. 2 110kV line power supply side circuit breaker 5DL corresponding to a 110kV bus PT4 of a power supply end 220kV transformer substation;

meanwhile, collecting the switching-on position information of a load side circuit breaker 2DL of a load side circuit-incoming line load side circuit breaker of a load end 110kV transformer substation II-section bus PT secondary A-phase voltage Ua2, B-phase voltage Ub2, C-phase voltage Uc2, open-delta voltage 3Uo2 and No. 2 110kV power supply,

conditions are as follows:

(2) the three-phase voltage of a 110kV bus at a power supply end of a No. 2 110kV line is symmetrical and normal, and the open triangular voltage 3Uo1 is 0;

when the conditions are all met, identifying and judging that the No. 2 110kV power supply line is broken, after delaying t1, performing broken line protection on 110kV in 110kV line protection of a power end 220kV transformer substation, tripping a No. 2 110kV power supply line power supply side circuit breaker 5DL, performing 110kV spare power automatic switching action by a load end 110kV transformer substation, starting to trip off the No. 2 110kV power supply incoming line circuit breaker 2DL, closing a spare power supply circuit breaker 1DL or 3DL, recovering a transformer losing a power supply to the spare power supply line for power supply, and starting No. 2 110kV line broken line alarm;

or when the conditions are all met, identifying and judging that the No. 2 110kV power supply line is broken, after a delay t1, performing disconnection protection on 110kV in the No. 2kV 110kV line protection of the load end 110kV transformer substation, jumping the No. 2kV power supply line load side circuit breaker 2DL, starting the closing of the standby power supply circuit breaker 1DL or 3DL by the 110kV spare power automatic switching action of the load end 110kV transformer substation, enabling the transformer losing the power supply to recover to the standby power supply line for supplying power, and starting No. 2kV 110kV line disconnection alarm;

1.3) when the 110kV line is broken, the tripping process is as follows:

(1) tripping off a breaker at the power supply side of the broken line;

(2) tripping off a circuit breaker on the load side of the broken line;

(3) the circuit breakers on both sides of the line break are tripped together.

2. The line disconnection protection method based on voltage vector difference and spare power automatic switching as claimed in claim 1, wherein the upper and lower limits of the setting value of the vector difference are 4-6V.

3. The line disconnection protection method based on voltage vector difference and spare power automatic switching as claimed in claim 1 or 2, wherein the t1 time is set to 0.1-0.2 seconds.

4. The method for line disconnect protection based on voltage vector difference and spare power automatic switching as claimed in claim 1, wherein the voltage data on both sides does not require synchronization.