RU2751541C1 - Method for protection of power transmission lines in case of unsuccessful single-phase re-activation - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: invention relates to electric power engineering in high-frequency protection of power transmission lines with phase-by-phase control of switches. To protect the line, a combined relay of the reverse sequence current and its emergency component is used. The parameters of relay operation are calculated from the signal of a single-phase automatic re-activation by the currents of the previous incomplete-phase mode. The parameters are adaptively entered into the current relay as setpoints to protect the line in the event of unsuccessful single-phase automatic re-activation of the disconnected phase.

EFFECT: ensuring the speed of switching off the power line in case of unsuccessful single-phase automatic re-activation.

1 cl, 1 dwg

Description

The invention relates to the electric power industry, in particular to relay protection and automation (RPA) of power transmission lines (LEP) in case of unsuccessful single-phase automatic reclosing (OAPV). Solves the problem of low speed in high frequency (HF) protection with absolute selectivity of transmission lines with unsuccessful single-phase line reclosing.

According to [1], it is necessary to install high-speed protections with absolute selectivity on high and extra-high voltage transmission lines with two-way power supply with phase-by-phase control of switches. The use of directional high-frequency protection (NHFZ) for these purposes turns out to be unacceptable due to the failure of such protection in open-phase modes of operation. In practice, the NVChZ in the open-phase mode is transferred to the phase-differential protection (DFZ) mode. However, as was shown in the monograph [2], the phase-differential principle fails to operate in case of complex types of damage on power lines, in particular, with the simultaneous presence of a break and a short circuit on the protected line. It is this mode that is obtained on a line with phase-by-phase control of switches with an unsuccessful OAPV on it.

Due to the fact that the phase-differential principle can refuse complex types of damage, additional relays are used for selective operation in case of an unsuccessful OAPV in phase-differential protection.

The closest to the claimed technical solution is the method described in [3], where it is proposed to use phase resistance relays to protect power lines, one of which is connected when a command is generated to re-enable the disconnected phase. This method is chosen as the prototype of the invention. Its disadvantage is that in case of an unsuccessful OAPV, the protection operation time is forced to adjust from the beat time. The frequency of natural oscillations of the OAPV switched off in the cycle on both sides of the damaged phase, at the ends of which there are shunt reactors, is close to the industrial frequency at which the power transmission line operates. Therefore, the delay for the operation of the resistance relay to protect the line in case of unsuccessful OAPV can be 100 ms or more.

The purpose of the invention is to ensure the speed of protection in case of unsuccessful OAPV on the power line. This goal is achieved by the fact that instead of a resistance relay in the RF protection logic circuit, for example, DFZ, an additional combined relay of the negative sequence current and its emergency component is used. The operating parameters of the combined current relay are adaptively formed according to the phase currents i _A , i _B , i _C of the open-phase mode of the OAPV cycle.

The implementation of the method is illustrated in FIG. a block diagram of the logic of the functioning of a semi-set of protection installed at one of the ends of the transmission line, which is included in operation with a single-phase automatic reclosing. The block diagram of FIG. contains the following modules and blocks: HF protection module (element 1), OAPV module (element 2), negative sequence filter (FOP) (element 3), block for generating adaptive response parameters (setting block) (element 4) and combined current relay negative sequence (CRT OP) (element 5), which will include a reverse sequence current relay (RTOP) (element 5.1), a filter of emergency components (FAS) (element 5.2), a reverse sequence current relay of an emergency component (RTOP AS) (element 5.3), an element of time to operate (element 5.4) and a logical element "AND" (element 5.5).

The method is carried out as follows.

In case of a single-phase short circuit in the protection zone on the power transmission line, HF protection semi-sets (element 1) are triggered at the ends of the power line, which start the OAPV modules (element 2) of their semi-sets. Accordingly, the OAPV module (element 2) detects the faulty phase, which is switched off at both ends of the line. The power transmission line goes into the non-full-phase mode of the OAPV cycle and generates the signal (2.1) "OAPV cycle".

The signal (2.1) "OAPV cycle" starts the FOP unit (element 3), which, according to the current phase currents i _A , i _B , i _C, forms a complex value of the negative sequence current I ₂ (signal 3.1). The magnitude of the negative sequence current I _{2 is} fed to two KRTOP relays (element 5). In the first reverse sequence current relay RTOP (element 5.1), the current modulus I ₂ is compared with the current adaptive setting (signal 4.1 - I _{2 set} ) coming from the setting block (element 4). The second relay KRT OP (element 5) consists of two elements: FAS (element 5.2), which forms the emergency components of the negative sequence current I _{2 av} [4], and the actual relay of the current emergency component of the reverse sequence RTOP AS (element 5.3), where comparison of the current value of the emergency component of the negative sequence current with the adaptive setting (signal 4.2 - I _{2 set} ), also coming from the setting block (element 4). Until the expiration of the OAPV cycle time and the appearance of the command to re-enable (signal 2.2 “Re-enable”), the SRT OP is blocked by means of a time element (element 5.4) and a logical element “AND” (element 5.5).

After the expiration of the OAPV cycle, the OAPV module (element 2) generates a command to re-close (signal 2.2) the breaker of the disconnected phase. At the same time, on the signal "Re-enable" (signal 2.2) in the setting block (element 4) for the current phase currents i _A , i _B , i _C of the open-phase mode of the OAPV cycle, the parameters of the operation of the negative sequence current I _{2 set} (signal 4.1) and its emergency component I _{2av set} (signal 4.2), which, as adaptive settings, are fed to the RTOP (element 5.1) and RTOP AS (element 5.3), respectively.

The “Re-enable” signal (signal 2.2) through the delay of the response time element (item 5.4) enables the operation of the SRT OP. The time delay (element 5.4) makes it possible to exclude the nonselective operation of the MCT OP due to interference at the moment of the circuit breaker phase re-closing, and also detaches itself from the short-term transient process arising in this mode.

In the case of a successful OAPV from the side of the line end, which is switched on first, in the HF protection semi-set, the negative sequence current I ₂ (signal 3.1) at the RTOP input (element 5.1) practically does not change and, as a consequence, the I ₂ module will certainly be less than the setting value I _{2 set} (signal 4.1) generated by the setting block (element 4), and the RTOP will not work. Similarly, a small change in the negative sequence current I ₂ at the input of the FAS filter (element 5.2) causes the value of the emergency current component I _{2 av to be almost zero} and, as a consequence, the absence of operation of the RTOP AS (element 5.3), the setting of which I _{2av set} (signal 4.2) is formed by the block of settings (element 4). Thus, the RTOP and RTOP AS relays on the logical element "I" (element 5.5) will block the disconnecting output signal "Disconnection of 3 phases" of the KRT OP relay.

In the case of a successful OAPV from the side of the end of the line, which turns on the second and closes the line in transit, a symmetrical system of phase currents i _A , i _B , i _C and the magnitude of the negative sequence current I ₂ (signal 3.1) are fed to the input of the RF protection semi-set. the input of the SRT OP (element 5) is close to zero, and, as a consequence, the module I ₂ at the input of the RTOP (element 5.1) will certainly be less than the value of the setpoint I _{2 set} (signal 4.1), formed by the setting block (element 4), the RTOP relay will not work and will block the disconnecting output signal of the KRT OP. In this case, a sharp change in the negative sequence current I ₂ during the transition to the symmetrical mode at the input of the FAS filter (element 5.2) causes the appearance of the value of the value of the emergency component of the current I _{2 av} , which can exceed the setting I _{2av set} (signal 4.2), and, as a consequence, trigger the RTOP AS relay (item 5.3). However, the disconnecting output signal "Disconnection of 3 phases" of the KRT OP relay is already blocked at the "I" element (element 5.5) by the RTOP signal (element 5.1).

When re-switching on for permanent damage or a repeated breakdown in the place of damage, an unsuccessful RPA mode will be observed.

In this mode, from the side of the line end, which is switched on first, in the HF protection semi-set, the negative sequence current I ₂ (signal 3.1) at the RTOP input (element 5.1) changes significantly and, as a consequence, the current module I ₂ will certainly be greater than the setting value I _{2 set} (signal 4.1), formed by the block of settings (element 4), which will trigger the RTOP. Similarly, a change in the negative sequence current I ₂ at the input of the FAS filter (element 5.2) causes the appearance of a significant value of the emergency component of the current I _{2 av} and, as a consequence, the operation of the RTOP AC relay (element 5.3), the setting of which I _{2av set} (signal 4.2) is formed by the block settings (element 4) by the values of the currents of the open-phase mode of the OAPV cycle. Thus, from the outputs of the RTOP and RTOP AS relays to the logical element "I" (element 5.5), the levels of the logical "1" arrive, and when the time delay of the element of time (element 5.4) expires, a tripping output signal "Disconnection of 3 phases" of the relay KRT appears. OP.

In the case of an unsuccessful OAPV from the side of the line end, which turns on the second and closes the line in transit, the negative sequence current value I ₂ (signal 3.1) arriving at the RTOP input (element 5.1) at the input of the HF protection semi-set (element 5.1) will change according to the inverse proportional law of equivalent negative sequence resistances electrical systems of the ends of the line, which practically differ little from each other and, as a consequence, the module I ₂ will be close to the same value of the opposite end of the line and, obviously, like the current of the negative sequence of the end of the line switched on first, will be greater than the value of the setting I _{2 set} (signal 4.1) formed by the block of settings (element 4). A similar situation will be observed with a change in the negative sequence current I ₂ at the input of the FAS filter (element 5.2), which will cause the appearance of a significant value of the emergency component of the current I _{2 av} and, as a consequence, the operation of the RTOP AS relay (element 5.3). Thus, from the outputs of the RTOP and RTOP AS relays to the logical element "I" (element 5.5), the levels of the logical "1" arrive, and when the time delay of the element of time (element 5.4) expires, a tripping output signal "Disconnection of 3 phases" of the relay KRT appears. OP of the second end of the line.

Thus, according to the principle of its action, the proposed method allows for high-speed protection for power lines with phase-by-phase control of switches to provide high-speed protection in case of unsuccessful OAPV, the settings of which are adaptively calculated according to the currents of the open-phase mode of the OAPV cycle.

Of particular interest is the calculation of the operation parameters (settings) of the current relays KRT OP: RTOP and RTOP AS. The value of the RTOP current relay setting mod ( I ₂ ) ≥I _{2 set} should be detuned from the current operating phase current mod ( I ₂ ) = ƒ (I _{tech phases} ) in the open-phase mode of the OAPV cycle. The negative sequence current setting for a phase A single-phase short circuit can be calculated as:

where I _B , I _C - currents of undamaged phases in the OAPV cycle;

I _A - virtual current in the third phase;

_Phase I incomplete Mode - module of the maximum primary phase load current at the place of protection installation in the open-phase mode of the OAPV cycle;

k _ot - offset coefficient, the maximum value of which can be taken equal to the required sensitivity coefficient k _ot = k _h required = 1.25.

To calculate the setting of the RTOP AS mod ( I _{2 av} ) ≥I 2av _set, it is necessary to calculate the modules of the currents of the negative sequence.

Setting RTOP AU alarm of negative sequence mod (I _2av) has to be rebuilt from the unbalances caused by the phase error measuring circuit in unbalance, and is calculated by the expression: mod (I _2av) ≥I _{2av mouth UTS} = k / k _a * I _nb ,

where: k _ot = 2.5 - offset coefficient; k _in = 0.95 - return coefficient;

I _2nb = (0.02 ÷ 0.05) * I _{phase incomplete mode} - primary unbalance current caused by an error

measuring path of the measuring current organ. For the case of maximum

errors of the measuring current transformer, the value of the setting for the emergency component will be equal to:

Thus, the settings of the relay KRT OP: RTOP and RTOP AS depend only on the value of the current maximum phase current and are equal, respectively:

I _{2 set} ≈0.42 * I _{phase incomplete mode} , I _{2av set} ≈0.14 * I _{phase incomplete mode} .

Sources of information

1. Rules for electrical installations, 7th ed., Approved. By order of the Ministry of Energy of Russia dated 08.07.2002 No. 204.

2. Atabekov GI Theoretical foundations of relay protection of high-voltage networks. M. Gosenergoizdat, 1957.

3. A cabinet for phase-differential line protection with a set of step protections and a single-phase automatic reclosing device TYPE SHE2710 582 Operation manual EKRA.656453.039-21 OM.

4. Patent 2035815 Russian Federation, MKI Н02Н 3/38. A method for isolating the emergency term of the short-circuit current / Yu.Ya. Lyamets, V.A. Efremov, V.A. Ilyin. Publ. 05/20/1995

Claims (1)

A method of high-frequency protection of a high voltage power transmission line with absolute selectivity with phase-by-phase control of switches, characterized by the fact that a short-time relay is used to protect the line in case of unsuccessful single-phase automatic reclosing, characterized in that in order to increase the speed of protection in the mode of unsuccessful single-phase automatic reclosing, a combined negative sequence current relay and its emergency component, the operation parameters of which are calculated according to the signal of single-phase automatic reclosing according to the currents of the previous open-phase mode and are adaptively entered as settings in the current relay to protect the line in case of unsuccessful single-phase automatic reclosing of the disconnected phase.

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