Permissible increase in the voltage of the industrial frequency of the equipment during operational switching and emergency operations

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Appendix 4. Permissible increase in the voltage of the industrial frequency of the equipment during operational switching and emergency operations. Encyclopedia of radio electronics and electrical engineering

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

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Table A.4.1

Equipment	Permissible increase in voltage during the duration of exposure, s
Equipment	1200	20	1	0,1
Power transformers and autotransformers*	1,10** 1,10	1,25 1,25	1,90 1,50	2,00 1,58
Shunt reactors and electromagnetic voltage transformers	1,15 1,15	1,35 1,35	2,00 1,50	2,10 1,58
Switching devices***, current transformers, coupling capacitors and bus supports	1,15 1,15	1,60 1,60	2,20 1,70	2,40 1,80
Valve arresters of all types	1,15	1,35	1,38	-
Surge arresters, non-linear	1,39	1,50	1,65	-

* Regardless of the values \u1200b\u1,15bspecified in the table, according to the condition of heating the magnetic circuit, the voltage increase in fractions of the rated voltage of the installed winding branch should be limited at 20 s to 1,3, at XNUMX s - up to XNUMX.

** The numerators show the values for the phase-to-ground insulation in fractions of the amplitude of the highest working phase voltage, in the denominators - for the phase-to-phase insulation in fractions of the amplitude of the highest working phase-to-phase voltage.

*** Regardless of the values specified in the table, the self-recovering voltage at the circuit breaker contacts must be limited by the condition of disconnecting the intact phase of the line in case of an unbalanced short circuit to 2,4 or 2,8, depending on the type of circuit breaker used.

The values for phase-to-phase isolation apply only to three-phase power transformers, shunt reactors and electromagnetic voltage transformers, as well as to devices in a three-pole version with three poles located in one tank or on one frame, while the values of 1,6, 1,7 and 1,8 apply only to external phase-to-phase insulation of devices with a voltage of 110 kV.

With a duration of voltage increase intermediate between the two values given in Table. 2.1, the allowable voltage rise is taken from the largest of these two values. At (0,1 < t < 0,5) s, a voltage increase equal to U1s + 0,3 (U0,1c - U1s) is allowed, where U1s and U0,1s are the allowable voltage increases for a duration of 1 and 0,1 s, respectively .

With the simultaneous effect of voltage increase on several types of equipment, the lowest value normalized for these types of equipment is acceptable for the electrical installation as a whole.

The number of voltage rises with a duration of 1200 s should be no more than 50 within 1 year, with a duration of 20 s - no more than 100 for the service life of electrical equipment specified in the state standard, or for 25 years if the service life is not specified. In this case, the number of voltage increases with a duration of 20 s should be no more than 15 for 1 year and no more than 2 - for 1 day.

The time interval between two voltage rises of 1200 and 20 s duration must be at least 1 hour. If a voltage increase with a duration of 1200 s occurred 2 times (with an hourly interval), then within the next 24 hours a third increase in voltage is allowed only in case of an emergency, but not earlier than after 4 hours.

The number of voltage rises with a duration of 0,1 and 1 s is not regulated. The number of voltage rises for valve arresters and surge arresters is also not regulated.

To prevent voltage rises beyond the allowable values, local regulations should specify the procedure for switching on and off each long 110 kV transmission line. For lines with a voltage of 110 kV, on which a voltage increase of more than 1,1 of the highest operating voltage is possible, relay protection against overvoltage should be provided.

In circuits, including starting ones, in which, during planned switching on of the power line, a voltage increase of more than 1,1 is possible, and with automatic shutdowns of more than 1,4 of the highest working one, it is recommended to provide automatic devices that limit the value and duration of the voltage increase to acceptable values.

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

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