SU1653051A1 - Three-phase high-voltage transmission line - Google Patents

Abstract

The invention can be used on high-voltage overhead power lines with high-frequency processing of cargo protection cables. The aim of the invention is to expand the area used for the transmission of cable frequencies and increase the reliability of the barriers. For this, the calculated grounding resistances of the line spores are chosen according to the law, determined on the basis of the newly obtained mathematical dependencies, taking into account the parameters of the network to which the line is connected, and the design of the line itself. The use of the proposed technical solution will allow refusing installation of additional barriers into the cable. 3 il. (L

Description

This invention relates to the power industry, in particular, to high voltage overhead lines (VL).

The aim of the invention is to improve the reliability of the layer, connected to the cables, by limiting to a safe amount the current flowing through these layers by single-phase short circuits on the overhead transmission line, and expanding the area used for transmission channels over the frequency cables.

FIG. 1 shows a circuit for connecting load protection cables of a power line;

figure 2 - dependences illustrating the operation of the circuit elements; FIG. 3 is a replacement scheme for calculating these dependencies.

With a single-phase short-circuit (short-circuit) on any support line two situations can be created:

the voltage on the air spark gap 1, shunting on this support a bush 2, on which the overhead protection cable 3 is suspended, does not exceed the breakdown voltage of this gap Unp;

the voltage on air gap 1 exceeds Unp.

about eaten with o

In the latter case, the gap 1 will be broken and part of the short-circuit current. go along cables 3 through high-frequency barriers 4 to the grounding devices of 5 substations. This current may exceed the value allowed for barriers and i.opd.

Therefore, the most favorable case for barriers is the first case. It is proposed to provide it by grounding the support 6 (Fig. 1) with a resistance not exceeding the value

tЈ o)

where Unp is the breakdown voltage of a spark gap shunting a cable wire of insulators:

} K - the maximum rated current of a single-phase short circuit. at damage on this support (actual value};

K-factor of safety (K 1,2 ,. .1,3).

The second mode may also be acceptable (with the breakdown of spark gaps), but provided that the ground resistance of the support on which a fault has occurred, is such that the current branching through the grouper 4 does not exceed the allowable one. For this, the ground resistance of the support should not exceed the value of

.li Zn p1 ZBX2 b dop Zaxi

Rd l3 "on (ZoTl + ZBx2) - k, ZUT, 12 / PG2

(2)

where H, la are the maximum single-phase short-circuit currents flowing to the damage point, respectively, from the first and second substations (effective values);

Zexl. ZBx2 the input resistances of the loops of the cable are the ground in the direction of the first and second substation, respectively, from the point of a short circuit;

2p.t.1, Zn.T.2 resistance of the electromagnetic connection between the wires of the line and cables from the short-circuit point. to the first and second substations respectively,

1 edop-permissible under the conditions of dynamic stability of the current through the layer.

Figure 2 shows characteristic curves of a single-phase short-circuit current change. along VL, where I is the value of the short circuit current; 11 and h are maximum short-circuit currents flowing in, respectively, from the sides of the first and second substations; Zdop - maximum full current short circuit; 1з1 and 1з2 - currents flowing through the grouser, respectively, at the first and second substations with normal ground resistance of the supports; 1zdop - the value of the current of the barrier, permissible by the condition of dynamic stability; I-length overhead; d is the distance from the first substation, at which the current through the minelayer at a given substation must be

excluded or limited; h is the same for the barrier at the second substation; ti and h are the distances from the tires, respectively, of the first and second substations, at which the current through

the layer should be excluded. ia 1 is the current flowing through the barrier in the first substation while reducing the support resistance in the area from t 1 to b to values determined by the formula (2), C is the same for the second substation.

Calculation formula for determining the single-phase short-circuit current. Lt flowing in the cable after the spark gap is broken on a support with damage to the insulation of the VL phase,

obtained from the replacement scheme shown in FIG. 3, where the designations are the same as in formula (2)

The single-phase current to c k is for this circuitry input. and the favorable ones in the cable are the voltage E 17, t 1 and E2 - IzZn t 2 sources of electromotive force of the first and second co.1 round x respectively Toki ij- | and | z2 are determined by the current distribution of Ir and the currents named EMF Ech and E-2

according to the laws of rhghoff, the parameters ZBx and Zn t are calculated from the lime Formulas

Fortune (2) t, ll {1 oppl lnp1 pelicinas I s1 semitones of y equals, d b and by

solutions; then fire models replace 31 with IJAO, i.

Thus, the choice of ground resistance of the supports according to the forms / llamas (1) and (9) ensures either the absence of a current of the minelayer when it is housed on the support of an additional third person with this current

In order to flOCTvDKenn the optimal cost of reducing the resistance of the ground loops of the supports of the resistance value

supports are calculated by the KJX d.d. and the VL supports by the formulas (1) and (2) and with the meanings, d (g, this is a large amount of resistance that requires less atra, but its implementation

the single-phase short circuit current decreases with distance from the VL ends, in the (0 - h) section (FIG. 2) the ground resistance of the supports, and in the section (i1 -1 (), on the contrary, Ra Ri (similar reasoning can be made

and for the magnitude of the grounding resistance of the supports on the side of the second substation in exactly the way, the boundary of the pers-run from R, (1) s RT is determined by the equality Rr, - R

Consequently, with mspol zoenii

the proposed principle of selecting the earths of the supports of the supports, none of them should not exceed the value normalized by the rules of the device system

; PUE).

The optimal solution is such that at a distance (up to 5 km) from substation busbars, the value of ground resistance of the supports should be taken according to

formula (1), and upon further removal, according to formula (2), the transition boundary being determined by equality of the values Ra and Ra. On those sections of the line where the calculated value of the grounding resistance according to the formula (2) becomes greater than that determined by the standards of the ПУЭ, the resistance of the grounding is accepted according to the norms of the ПУЭ.

Claims (1)

Claims of the Invention Three-phase high-voltage power lines containing insulated ground wire, wires of insulators of which are shunted by spark gaps, and high-frequency barrier through which the cables are grounded at the ends of the line at the first and second substations, characterized by , in order to improve the reliability of the barriers by limiting the current flowing through them during a short circuit on the line, and expanding the area used for transmission channels over the frequency cables, grounding to each line support is made with a resistance not exceeding the larger of the values NzRR1: R  3 R to  And Zn T1 - Zd Z "x1 Ldop (ZBX + ZBI, 2) - U Z, x2 - h Zw, + 12 ZnQ where IK is the maximum rated current of a single-phase short circuit. in case of damage on the support in question (effective value); 11 and 12 - maximum single-phase short-circuit currents flowing to the point of damage, respectively, from the first and second substations (effective values); ZBxi and ZBx2 are the input resistances of the loops of the cable — ground in the direction of the first and second substations, respectively, from the short-circuit point; Zn.r.1 and Zn.r.2 - resistance of the electromagnetic connection between the wires of the line and the cable from the short-circuit point. to the first and second substations, respectively; w.dop is the current allowed by the conditions of dynamic stability through the layer; Unp is the breakdown voltage of a spark gap shunting a cable girdle of insulators; R is the safety factor. Have  Vs  6 Phage.1 6 FIG. 2