SU864413A1 - Device for protecting balance-type of parallel power transmission lines - Google Patents

Description

The invention relates to devices for relay protection, in particular protection of parallel lines, and can be applied in substations and power stations. The transverse differential directions of protection are known for the accelerated disconnection of damages on one of the parallel lines l, l2 W and D4. Also known is transverse differential current protection of the balanced type 5. However, these devices require special block contacts on the switch shafts, as well as special plates requiring relatively frequent manipulation from the personnel on duty, mentioned protection can malfunction when the wires are broken. short circuit, and when the cascade off some types of double earth circuit. The purpose of the invention is to increase the reliability, sensitivity and expansion of the field of application of the device. This goal is achieved by the fact that in the device containing current transformers, current and power direction relays on each line, current directional balanced relays, whose inputs are connected to the transformer secondary windings :. current and neighbor line, time and power direction relays to the operational power source and intermediate relays, whose contacts are included in the circuit breaker tripping line switches, the first contact of the balanced relay is connected between the current relay contact and the winding of the output intermediate relay of the current directional protection of the neighboring line and the second contact of the current balanced relay is connected between the contact of the current direction relay and the winding of the output intermediate relay of the current directional protection of its line. FIG. 1 is a schematic diagram of one phase of the proposed device; in fig. 2 shows an example of execution of a directional current balanced relay Lp. At substation A (Fig. 1), the device contains directional current balanced relays 1 and 2. Hereinafter, the odd elements (Fig. 1) relate to line C, and even ones - to line 0. KBnt contacts 2 and 3 mention the balanced balance relays contacts of the first type., and contacts 5 and 6 - of the second type. Contacts 7 and 8 belong to the current relay and contacts 9 and 10 to the directional relay of current protection of the lines {Cu 0, respectively. Output intermediate relays 1 and 12 belong to the high-speed current protection of lines C and D, respectively, and relays 13 and 14 of time are current directed protection of the same lines. On line C (Fig. 1), the overcurrent protection can occur either via contact 4 of the first type, belonging to the balanced relay 2 and connected besides contact 9 of the directional relay between contact 7 of the current relay and the winding of the output relay 11, or through contact 5 of the second type, at its own balanced, relay 1 and connected through the contact 9, the directional relay between said contact 7 and the winding of the relay 11. On the line O, the current protection is accelerated in the same way: either through contact 3 of the first type belonging to the balanced relay 1 in addition to the contact 10, the direction relay between the current relay 8 contact and the winding of the output relay 12, or through the second type contact b, belonging to its balanced relay 2 and connected to the direction relay between the contact 8 and the relay 12 winding through contact 10 The proposed protection at the substation B. In the directional current bgitansnom relay (basic circuit) L, its inclusion corresponds to relay 1 (see figure 1). The protection device of the balanced type works as follows. If a balanced 1 has current 1, the other line coincides in phase with the current 1 of its line and exceeds it in magnitude, then contact 3 of the first type closes. When a balanced relay 1 has a current difference of 12 DRUES: a goy line and a fraction of its current line opposite in phase exceeds the current li in magnitude, contact 5 of the second type will close. In the absence of one of the currents 1 in this balanced relay, none of its contacts can be closed. Consider the following cases. 1. A short circuit outside the parallel lines or a load from the sides of the B. substation. Both parallel lines are the same and directed. To the substation A from buses, and to the substation B to buses. Protection devices at both substations do not create an incorrect acceleration of current directional protection. This is because for contacts of the first type in both substations, the current of the other line, taken with a coefficient less than one, is less than the current of its line, and for contacts of the second type, the current difference of the other line and the proportion of its own line in phase is less than the current of its line and coincides with it in phase, in addition, at the substation B, the contacts of the current protection direction relay, which controls the acceleration circuits, are open. 2. As in clause 1 of the job description or other conditions, and there is no current in one of the parallel lines, a short circuit with a broken wire or a cascade disconnect of the double ground circuit when one phase closes in the zone of parallel lines and the other outside their zone . Since there is no one of the currents, the balanced current directional relays in the proposed device cannot operate and the device does not create an incorrect acceleration of the current directional protection. 3. A short circuit (short-circuit) on the line D. I At the substation A, the currents 2. C are directed from the busbars, the current 1 being greater than the current C. Under these conditions, contact 3 of the first type is closed in the balanced relay 1 of line C and creates the correct acceleration of the current protection of the line D, which is not controlled by contact 10 of the directional relay and therefore does not have a dead zone in voltage. On line C of the balance relay 1, pin 5 of the second type cannot operate (close), because the difference between the high current 1 of the other line is in phase with the current C. On line D of the balance relay 2, pin 6 of the second type cannot operate, because the difference between the lower current I-, another line and the fraction of the current 2 of its line coinciding in phase or coincides in phase with the current 12, or, having the opposite phase, is less current 12. At substation B, it is necessary for the damaged line under these conditions to have a current I / 2. sent from the bus to the line, and the current 1 - to the substation bus. With one-way power from substation A and in the absence of load at substation B, these currents are the same in size, with the same power and load at substation B, the current I- is a little more than 1, and when the power supply is two-sided, Ig can be more than 1. For all the above mentioned ratios of currents 1 to g at substation B, for a damaged line, the difference between the current of the other line and the fraction of its current line 6jbina opposite in phase would be greater than the current of its line and opposite in phase. Due to this, at jn od station B and the balanced relay 2 lines O, contact 6 of the second type is closed, and at the balanced relay 1 of line C also contact 5 of the same type is closed. Since on line C

Substation B opens contact 9 of the current protection relay, then the current protection of this line will not accelerate. On the line L of the same sub-station, the contact TO the directional relay is closed, as a result of which the closed contact b of the second type creates the correct acceleration of the current protection of the line D. At the substation B, contacts 3 and 4 of the first type of balanced relays 1 and 2 of lines C and O cannot close. because currents 1 and G1 are in antiphase.

4, Special cases k.z. on line 0.

a) Кз, near the substation B. If the condition at the substation A is not satisfied: the current Ij is larger than the current I /

it happens first

disconnecting line D at substation B, and then cascading at substation A. In the case of single-sided power from substation A, balanced relay 1 at substation A closes its contact 3 of the first type and creates an accelerated disconnect circuit of line D. provided that With the load current remains. In this mode, resistors 30 may be required (see fig. 2 for reducing too large phase shifts between the fault current U and the load current 1.

b) K.z, near the substation A. With two-way power, the operation of the devices is similar to item 4a, but the conditions for the flow of currents relative to the substation will change. With one-way power from substation A, current 1 on line C may be so small that pin 3 of the first type of the balance relay in the set of substation A does not work, in the absence of one of the currents. In this case, the proposed protection device of the balanced type has a dead zone, and after the current cut-off of line D triggered at the substation

And the proposed device cascadingly provides an accelerated disconnection of line D at substation B, in addition, increasing reliability due to the absence of special block contacts on the shafts of switches and special linings requiring relatively frequent manipulations of personnel on duty,

c) K.z. in the middle of the line D. Under these conditions, with two-sided symmetrical power supply from the coinciding EMF, as well as with the same resistances and loads on both sides, it is possible, although unlikely, that the current line C and therefore, the proposed device fails to work, but continues to work again after one of the D line circuit breakers is disconnected from the current cutoff. There may be other versions of a balanced current relay that satisfies the requirements of this balanced type protection device. In those cases when balanced protection is installed only in the place of unilateral power supply of parallel lines, the single-phase balanced current relay with the possibility of operation only in the presence of both currents and with the contact of the first type can be completely undirected. This balanced type protection device has the following advantages over the known ones: increased reliability due to Sa; no abnormal actions during short circuits with wire breaks, as well as in the cascade disconnection of the double ground circuit, when one phase is damaged in the zone of parallel lines, and the other - outside their zone, an increase in sensitivity due to the fact that this device cannot act falsely if there is no current in one of the lines and only works if there is damage

0 in the zone of parallel lines, accelerated current protection with time delay, which require a lower reliability coefficient for tuning from the motor self-starting currents than the starting ones

f current protection organs without time delay, and also known current balancing protection ts. Expansion The application area of the device L5j can only be installed from the side of the substations associated with permanently switched on power sources of sufficiently high power, and this device does not require such a limitation.

Claims (5)

The invention is a device for protection of a balanced type of parallel power lines, which contains current transformers, current relays and power directions relays, current directional balanced relays, whose inputs are connected to the second windings of their own and neighboring current transformers, time relays, windings of which are connected through current contacts relays and relays of power direction to the operational source and intermediate relays, whose contacts are included in the circuit breaker disconnecting lines, characterized in that, in order to increase reliability, sensitivity and expand the scope, the first contact of the current balanced relay is connected between the contact of the current relay and winding output intermediate the current relay directional protection of the neighboring line, and the second contact of the balanced relay is connected between the contact of the direction relay and the winding of the output intermediate relay current directional defense of your line. Sources of information taken into account in the examination 1. Fedoseev A, M, Fundamentals of Relay Protection, Gosenergoizdat, 1961, p. 244 rice, 5-24. 2. Copyright certificate SSR 9 44412B, cl. G 01 R 25/00, 1974. 3. USSR author's certificate 603044, cl. H 02 H 3/40, 1978. 4. USSR author's certificate number 192292, cl. G 01 R 25/00, 1967. 5. Fedoseev A.M. Fundamentals of relay protection. Gosenergoiedat, 1961, p.252, fig. 5-32. /. /, (pite.l