RU2343616C1 - Method for inhibit of automatic switchover for voltage falls under conditions of unacceptable power surges - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention is related to electric system automation. Power at supply transformer input and value of load in bus system connected to restore power supply from undamaged input using automatic switchover (AS) switch is registered. Then controlled values are compared to evaluate if additional load capacity of backup system is sufficient and when reserve capacity does not cover the value of load being connected the signal for AS inhibition is generated.

EFFECT: enhancement of application field and functionality for the method by its using for inhibition of backup power supply automatic switching-on for voltage falls in buses of two-transformer step-down substations, and in minimisation of frequency and limitation of development dynamics of voltage falls at failing section side and in backup system.

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Description

The invention relates to the automation of electrical networks and is aimed at prohibiting the automatic switching on of a reserve (ATS) for voltage dips on bus sections of two-transformer step-down substations with unacceptable power surges of a reserved network section in order to limit the frequency of occurrence of dips and to increase the reliability of operation of power supply systems.

In existing power supply systems, equipment and current-carrying elements are usually designed only for rated currents. The load connection can be accompanied by power surges if the backup system does not have sufficient reserves, which will necessarily cause a power failure.

There is a method of prohibiting substation automatic turning on of a reserve for a stable short circuit, namely, that they fix the short circuit current at the input of the supply transformer between the input switch and the ABP switch, after its disappearance, the time of a non-current pause of the automatic restart (AR) of the input switch is counted, and if at the end of the count, the short circuit current does not disappear, then a signal is issued to prohibit the operation of the sectional breaker ABP [1].

The disadvantage of this method is that it does not take into account possible emergency conditions caused by unacceptable load surges of the bus system connected to the backup input, during which voltage drops occur in the system, both on the side of the emergency network section and on the backup section, which leads to power outages. The proposed method provides for limiting the frequency of voltage dips and their dynamics. The implementation of the method does not require structural changes in the topology of the existing power supply systems and equipment replacement.

The objective of the invention is to expand the scope and functionality of the method by using it to prohibit automatically turning on the backup power supply for voltage dips on the buses of step-down substations in the presence of an automatic reclosure input circuit breaker, as well as minimizing the frequency, limiting the dynamics of the development of voltage dips in the power supply system.

The method of prohibiting automatic switching on of the reserve (ATS) for voltage dips (MV) with unacceptable power surges consists in fixing the power of the connected emergency load and the power of the backup system. The method is characterized in that the reserve power reserve of the backup source at the input of the supply transformer and the load of the main source on the busbar sections of the step-down substation to the outgoing lines are fixed. In the event of an emergency, when it is required to implement redundancy with the help of an automatic transfer switch of a sectional switch, the power ratio in the load nodes is determined. On this basis, they conclude that the additional load capacity of the backup input is sufficient to connect the emergency section of the main source network without a voltage drop, and when the reserve is insufficient, a signal is issued to prohibit the automatic transfer switch.

The drawing shows a diagram of the prohibition of ATS on voltage dips with unacceptable power surges of the emergency network section. The ban scheme contains two independent inputs No. 1 and No. 2 operating in parallel (elements 1 and 2), supply transformers 1T and 2T (elements 3 and 4), an input switch for input No. 1 Q ₂ (element 5), an input switch for input No. 2 Q ₄ (element 6), bus sections I and II (elements 7 and 8), section switch ABP Q ₇ (element 9), load switches on the outgoing lines (elements 10, 11, 12, 13), power monitoring units for the allocated load for each input (BKM1 and BKM2, elements 14 and 15), power reserve control units of the connected source of bus sections (BKR1 and BKR2, elements 16 and 17), but data comparisons (WHSD, element 18), a parameter processing device (OOP, element 19).

The scheme works as follows. In normal mode, an operating current flows at the inputs of transformers 1T, 2T (elements 3, 4) and busbar sections I, II (elements 7, 8). Since the currents on the bus sections are not equal to the short circuit current (short circuit), the entire system of control units is not subjected to signals from the relay protection of the input switches Q ₂ or Q ₄ (elements 5 and 6), which are equipped with an automatic reclosing device (AR), as a result, the circuit does not start.

In the event of a short circuit in the section of the busbar section I behind switch Q ₂ (element 5), the protection puts it out of operation. At this moment, the BKM1 block (element 14) fixes the value of the power of the allocated load and issues this value to the WHSD (element 18) in the form P _working.s.I = m _I. At the same time, the BKR2 block (element 17) determines the power reserve in the backup system and then gives the command P _{res.II. II} = n _II to the data comparison link (element 18), where the check of compliance with the power levels at the load nodes is implemented : m _I ≈n _II . In the case when the reserve is not enough to connect the emergency section of the network without voltage surge, the ZSD will send a command to the parameter processing device in the form of a signal: m _I >> n _II , which indicates the danger of a voltage dip. Then, the circuit breaker is automatically turned on again (element 5) with the set shutter speed t of _{reclosure (Q2)} . OOP (element 19) produces a delay in time t _UOP equal to a dead time pause of reclosure: t _ROP = t _{reclosure (Q2)} , which coincides with the moment the signal arrives from the data comparison link. Therefore, the parameter processing device generates and gives a command to prohibit ATS and Q ₇ operation (element 9). When normal mode is restored, a voltage will appear on the busbar section I (element 7), which will be recorded by the executive bodies and the logical part of the ATS, and the circuit will return to its original state.

The proposed method of prohibiting the automatic inclusion of a reserve for voltage dips with unacceptable power surges was tested under production conditions at a step-down substation 110/10/6 kV of Lipetskenergo OJSC. The experiment confirmed the correctness of the method and the relevance of its implementation, and also allowed to determine the magnitude of the dips depending on the distance of the load nodes from the power source.

Thus, the ban on turning on the ATS section switch at a two-transformer substation is only applied when the backup system does not have sufficient power reserves to cover power surges of the load nodes connected in emergency mode, which prevents the ATS from switching on to voltage dips, and this increases the life of electrical equipment and live parts on the backup section. The method is applicable to ABP means of both single and double acting, and the principle of joint operation of control units does not change.

Literature

1. Pat. 2173017 Russian Federation, IPC Н02J 9/06, 13/00. A method of prohibiting the automatic inclusion of a reserve for a stable three-phase short circuit on the substation buses [Text]. / Vasiliev V.G .; Applicant and patent holder Oryol State Agrarian University. - No. 2000105132/09; declared 03/01/2000. - 6 p.

Claims (1)

A method of prohibiting automatic inclusion of a reserve (ATS) for voltage dips (MV) with unacceptable power surges, which consists in fixing the power of the connected emergency load and the power of the backup system, characterized in that the reserve power reserve of the backup source at the input of the supply transformer and the load of the main source are fixed bus sections of the step-down substation to the outgoing lines, and in case of an emergency when it is required to implement redundancy with the help of an automatic transfer switch of a section switch, I determine t is the ratio of capacities in the load nodes, from which they conclude that the additional load capacity of the backup input is sufficient to connect the emergency section of the main source network without voltage failure, and when the reserve is insufficient, a signal is issued to prohibit ABP.