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Section 2. Electrical equipment and electrical installations for general purposes

Chapter 2.8. Surge protection

Encyclopedia of radio electronics and electrical engineering / Rules for the technical operation of consumer electrical installations (PTE)

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2.8.1. Electrical installations of Consumers must have protection against lightning and internal overvoltages, made in accordance with the requirements of the rules for the installation of electrical installations.

Power transmission lines, outdoor switchgear, switchgear, switchgears and substations are protected from direct lightning strikes and lightning surges coming from the power transmission line. Protection of ZRU buildings and closed substations, as well as buildings and structures located on the territory of substations (oil facilities, electrolysis, tanks with flammable liquids or gases, etc.) is carried out in accordance with the established requirements.

2.8.2. Upon acceptance after installation of lightning protection devices, the following technical documentation must be transferred to the Consumer:

2.8.3. Consumers must store the following systematized data:

For each outdoor switchgear, the outlines of the protective zones of lightning rods, searchlight masts, metal and reinforced concrete structures, into the zones of which open current-carrying parts fall, must be drawn up.

2.8.4. Suspension of wires of overhead lines with a voltage of up to 1000 V (lighting, telephone, etc.) on outdoor switchgear structures, free-standing lightning rods, searchlight masts, chimneys and cooling towers and the supply of these lines to these structures, as well as the supply of these lines to explosive premises is not allowed.

The specified lines must be carried out by cables with a metal sheath in the ground. Cable sheaths must be grounded. The connection of lines to explosive premises must be carried out taking into account the requirements of the current instructions for the lightning protection of buildings and structures.

2.8.5. Every year before the thunderstorm season, the state of the overvoltage protection of switchgear and power transmission lines should be checked and the readiness of protection against lightning and internal overvoltages should be ensured.

Consumers should register cases of lightning outages and damage to overhead lines, switchgear and transformer substation equipment. Based on the data obtained, an assessment of the reliability of lightning protection should be carried out and, if necessary, measures should be developed to improve its reliability.

When installing non-standard devices or equipment in the switchgear, it is necessary to develop appropriate lightning protection measures.

2.8.6. Valve arresters and surge arresters of all voltages must be permanently switched on.

Switching off for the winter period (or some of its months) valve arresters, designed only for protection against lightning surges in areas with hurricane winds, ice, sudden temperature changes and intense pollution, is allowed in the outdoor switchgear.

2.8.7. Preventive testing of valve and tubular arresters, as well as surge arresters, must be carried out in accordance with the standards for testing electrical equipment (Appendix 3).

2.8.8. Tubular arresters and protective gaps should be inspected when bypassing power lines. The operation of the arresters is noted in the bypass sheets. Testing of tubular arresters with removal from supports is carried out 1 time in 3 years.

Mounting inspection without dismantling, as well as additional inspections and checks of tubular arresters installed in areas of intense pollution, must be carried out in accordance with the requirements of local regulations.

Repair of tubular arresters shall be carried out as necessary, depending on the results of checks and inspections.

2.8.9. Inspection of overvoltage protection equipment at substations should be carried out:

in installations with constant personnel on duty - during regular rounds, as well as after each thunderstorm that caused the operation of relay protection on outgoing overhead lines;

in installations without constant duty of personnel - during inspections of all equipment.

2.8.10. On overhead lines with a voltage of up to 1000 V, before the thunderstorm season, selectively, at the discretion of the Consumer responsible for the electrical economy, the serviceability of the grounding of hooks and pins of insulators installed on reinforced concrete supports, as well as the fittings of these supports, should be checked. In the presence of a neutral wire, the zeroing of these elements is also controlled.

On overhead lines built on wooden poles, the grounding and zeroing of the hooks and insulator pins on the poles with protection against lightning surges are checked, as well as where the neutral wire is re-grounded.

2.8.11. In networks with isolated neutral or with compensation of capacitive currents, operation of overhead and cable power lines with a ground fault is allowed until the damage is eliminated.

At the same time, the search for a place of damage on overhead lines passing in a populated area, where there is a danger of electric shock to people and animals, should be started immediately and the damage should be eliminated as soon as possible.

If there is a ground fault in the network at the moment, switching off the arc-suppressing reactors is not allowed. In electrical networks with increased requirements for the electrical safety of people (organizations of the mining industry, peat extraction, etc.), work with a single-phase ground fault is not allowed. In these networks, all lines outgoing from the substation must be equipped with earth fault protection.

2.8.12. In generator voltage networks, as well as in networks to which high-voltage electric motors are connected, when a single-phase short circuit occurs in the stator winding, the machine should automatically disconnect from the network if the earth fault current exceeds 5 A. If the fault current does not exceed 5 A, operation is allowed no more than 2 hours, after which the machine must be turned off. If it is established that the place of the ground fault is not in the stator winding, at the discretion of the technical manager of the Consumer, it is allowed to operate the rotating machine with a ground fault in the network for up to 6 hours.

2.8.13. Compensation of capacitive earth fault current by arcing reactors shall be used for capacitive currents exceeding the following values:

In networks with a voltage of 6 - 35 kV with overhead lines on reinforced concrete and metal supports, arc extinguishers are used with a capacitive earth fault current of more than 10 A.

The operation of networks with a voltage of 6 - 35 kV without compensation for capacitive current at its values ​​exceeding those indicated above is not allowed.

To compensate for the capacitive earth fault current in the networks, grounding arc-suppressing reactors with automatic or manual current regulation should be used.

Measurements of capacitive currents, currents of arcing reactors, earth fault currents and neutral displacement voltages should be carried out during commissioning of arcing reactors and with significant changes in the operating modes of the network, but at least once every 1 years.

2.8.14. The power of arc extinguishing reactors should be selected according to the capacitive current of the network, taking into account its future development.

Grounding arc extinguishing reactors must be installed at substations connected to the compensated network by at least two power lines. Installation of reactors at dead-end substations is not allowed.

Arcing reactors must be connected to transformer neutrals through disconnectors.

To connect arcing reactors, as a rule, transformers with a star-delta winding connection must be used.

Connection of arcing reactors to transformers protected by fuses is not allowed.

The input of the arcing reactor intended for grounding must be connected to a common grounding device through a current transformer.

2.8.15. Arc suppression reactors must be resonantly tuned.

Adjustment with overcompensation is allowed, in which the reactive component of the earth fault current should be no more than 5 A, and the degree of detuning should be no more than 5%. If arc-suppressing reactors installed in a network with a voltage of 6 ¸ 20 kV have a large difference in the currents of adjacent branches, it is allowed to adjust with a reactive component of the earth fault current of not more than 10 A. In networks with a voltage of 35 kV at a capacitive current of less than 15 A, a detuning degree of not more than 10% is allowed . The use of settings with undercompensation is allowed temporarily, provided that emergency unbalances in the capacitances of the network phases (for example, when a wire breaks) lead to the appearance of a neutral displacement voltage that does not exceed 70% of the phase voltage.

2.8.16. In networks operating with capacitive current compensation, the unbalance voltage should not exceed 0,75% of the phase voltage.

In the absence of a ground fault in the network, the neutral bias voltage is allowed not higher than 15% of the phase voltage for a long time and not higher than 30% for 1 hour.

Reducing the voltage of unbalance and displacement of the neutral to the specified values ​​should be carried out by equalizing the capacitances of the network phases relative to the ground (changing the relative position of the phase wires, distributing high-frequency coupling capacitors between the phases of the lines).

When connecting high-frequency coupling capacitors and lightning protection capacitors of rotating machines to the network, the admissibility of the asymmetry of the phase capacitances relative to earth must be checked.

Phase-by-phase switching on and off of overhead and cable power lines, which can lead to a neutral displacement voltage exceeding the specified values, is not allowed.

2.8.17. In networks with a voltage of 6 ¸ 10 kV, as a rule, smoothly adjustable arcing reactors with automatic adjustment of the compensation current should be used.

When using arc-suppression reactors with manual current control, the setting values ​​​​should be determined by the compensation detuning meter. If such a device is not available, the settings should be selected based on the results of measurements of earth fault currents, capacitive currents, compensation current, taking into account the neutral displacement voltage.

2.8.18. In installations with vacuum circuit breakers, as a rule, measures must be taken to protect against switching overvoltages. Rejection of surge protection must be justified.

2.8.19. A consumer powered by a network operating with capacitive current compensation must promptly notify the operating personnel of the power system about changes in its network diagram for the restructuring of arc-suppression reactors.

2.8.20. At substations with a voltage of 110 ¸ 220 kV, in order to prevent the occurrence of overvoltages from spontaneous displacements of the neutral or dangerous ferroresonant processes, operational actions should begin with grounding the neutral of the transformer, which is included in an unloaded busbar system with voltage transformers NKF-110 and NKF-220.

Before separating from the network an unloaded busbar system with transformers of the NKF-110 and NKF-220 types, the neutral of the supply transformer must be grounded.

150 ¸ 220 kV switchgear with electromagnetic voltage transformers and switches, the contacts of which are shunted by capacitors, must be checked for the possibility of ferroresonant overvoltages during busbar system disconnections. If necessary, measures should be taken to prevent ferroresonant processes during operational and automatic shutdowns.

In networks and connections with a voltage of 6 ¸ 35 kV, if necessary, measures must be taken to prevent ferroresonant processes, including spontaneous displacements of the neutral.

2.8.21. Unused windings of the low (medium) voltage of transformers and autotransformers must be connected in a star or delta and protected from overvoltages.

Protection is not required if a cable power line of at least 30 m in length is permanently connected to the low voltage winding.

In other cases, the protection of unused low and medium voltage windings must be made by earthing one phase or neutral, or by valve arresters or surge suppressors connected to the output of each phase.

2.8.22. In networks with a voltage of 110 kV, the neutral grounding of the windings with a voltage of 110 kV of transformers, as well as the logic of the operation of relay protection and automation, must be carried out in such a way that during various operational and automatic shutdowns, network sections without transformers with grounded neutrals are not allocated.

Overvoltage protection of the transformer neutral with an insulation level lower than that of the line bushings must be provided by valve arresters or surge suppressors.

2.8.23. In networks with a voltage of 110 kV during operational switching and in emergency modes, the increase in the voltage of industrial frequency (50 Hz) on the equipment should be within the values ​​\u4.1b\u4bgiven in Table. Clause 50 (Appendix XNUMX). The specified values ​​also apply to the amplitude of the voltage formed by superimposing the XNUMX Hz sinusoid with components of a different frequency.

See other articles Section Rules for the technical operation of consumer electrical installations (PTE).

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