RU2542742C1 - Method of emergency load limitation in power distribution network - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: in case of emergency in the network pulse-time coded commands for switching off are set for non-essential consumers, the station operating in emergency mode to the isolated network section is selected, in switchgear with voltage 10(6)-20 kV at the transmitting end of the line passing from the selected station in case of emergency power circuit breakers are switched off for a short moment and switched on and power supply interruptions of different fixed duration are created at actuators related to this line of power consumers, in switchgear of a lower voltage level these interruptions are received as pulse-time coded commands and upon their identification power switches of non-essential consumers are switched off on a selective basis.

EFFECT: improved reliability of power supply for essential consumers.

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Description

The invention relates to the field of electricity and is intended for use in the implementation of reliable power supply to responsible consumers of electricity, including in a system with its own source.

The logic of the functioning of existing emergency control devices provides for automatic dosing of control actions, including the shutdown of all electrical connections of power receiving installations of consumers of electricity with the power system, as well as the prohibition of automatically entering the reserve of disconnected communications. At the same time, responsible consumers of electricity are often disconnected. Such outages are inevitable even if they are supplied from their own source (distributed generation source), which in modern market conditions with an increasing tendency to regulate prices (tariffs) for electricity transmission services based on such parameters as reliability and quality of customer service in accordance with international indicators SAIFI, SAIDI, CA1F1, CAIDI, becomes not acceptable.

Among the main reasons for disconnection by emergency control devices of critical high-tech power consumers in emergency conditions, including when allocating an own source to a balanced load, the following can be distinguished:

- disconnections in distribution networks, as a rule, occur at a voltage level of 10 (6) -20 kV, where both non-responsible and responsible consumers of electricity are usually connected to disconnected feeders (intermittently);

- the calculated power to disconnect the load from existing emergency control devices is usually taken with a margin that takes into account the maximum power imbalance, while the excess load is disconnected;

- low dynamic stability of own sources in comparison with large generators of power plants does not exclude the risk of completely paying off the load supplied by the own source, since the inertia constant of a single-shaft gas turbine installation (Tj = 11-15 s) of small generation is several times smaller than the constant of inertia of such installations of high power (100 MW or more (Tj> 30 s)) and own sources are slowed down or accelerated faster with unbalances.

To ensure reliable power supply to responsible consumers, it is necessary to implement the transfer of control commands from emergency control devices only to disconnect non-responsible consumers. This is possible if the control action approaches the installation site of non-responsible energy consumers, that is, deep into the distribution networks, as a rule, at a voltage level of 0.4 kV in the metropolitan area.

It is known “Device for guaranteed power supply of responsible consumers”, described in patent RU 2410816, IPC H02J 9/04, publ. 01/27/2011, in which in the event of an emergency shutdown of an autonomous power station and until the start of the backup diesel generator, the load of responsible consumers (non-disconnecting) is assumed by the uninterruptible power supply or battery. After start-up, the standby diesel generator starts to work in a possible power shortage mode, while a slow decrease in the speed of the standby diesel generator occurs. To restore the nominal speed and voltage of the backup diesel generator, the first stage of the frequency unloading of means for automatically switching off consumers is activated. At the same time, non-responsible consumers are disconnected, and the power shortage is reduced. If the disconnection of these consumers is insufficient and the frequency continues to decrease, the next stage of frequency unloading is disabled. The number of steps of frequency unloading is determined in each case as necessary.

However, the laying of separate dedicated power lines directly to the responsible consumers of electricity, eliminating the need for transmitting and receiving devices, but requiring significant material costs and not allowing to turn off the non-responsive load that is part of the responsible consumers of electricity.

The well-known “Communication method over power lines for electric power transmission networks” (see US patent No. 7952846, IPC Н02Н 3/00, published May 31, 2011), commands are sent to disconnect non-responsible consumers deep into distribution networks (at voltage level 0, 4 kV) using communication channels.

However, although sufficient reliability is provided in the power supply to responsible consumers of electricity, there is a problem in terms of technical and economic indicators.

The most promising direction in this regard is characterized by the transfer of commands to disconnect non-responsible consumers deep into distribution networks (including the voltage level of 0.4 kV) without the use of communication channels.

The closest in technical essence is the “Uninterruptible Power Supply for Responsible Consumers” described in RF Patent No. 2321936, IPC H02J 9/06, publ. 04/10/2008, in which disconnection of an irresponsible load is selectively carried out, including when allocating an own source to a balanced load and own needs. In the event of an emergency shutdown of a three-phase network, the generator begins to work in a possible mode of power shortage up to 50%, while a slow decrease in the frequency of rotation of the generator occurs (the speed of falling speed is higher, the greater the power shortage). To restore the nominal speed and voltage of the generator, the first stage of the frequency unloading of means for automatically switching off non-responsible consumers is triggered. At the same time, non-responsible consumers are disconnected, and the power shortage is reduced. If the disconnection of these consumers is insufficient and the frequency continues to decrease, the next stage of frequency unloading is disabled.

The disadvantage of this method is the low reliability and the likelihood of maintaining power supply to responsible consumers of electricity.

The technical result of the invention is to increase the reliability and preservation of power supply for responsible consumers of electricity and the implementation of emergency load limits in the power distribution network with selective disconnection of a dispersed set of non-responsible consumers of electricity.

This result is achieved by the fact that the known method of emergency load limitation in the power distribution network, including a priori division of electricity consumers into responsible and non-responsible, characterized in that in the event of an accident in the network, time-code codes for shutdown are set for non-responsible consumers, and a power station operating in emergency operation on an isolated load of a network section in a switchgear located at the transmitting end of the line extending from the outlet In the event of an accident, the circuit breakers are briefly turned off and turned on and interruptions of power supply of various fixed durations are created on the actuators of all consumers of electricity connected with this line, in the switchgear of a lower voltage level, these interruptions of power supply are perceived as time-pulse code commands and, after their recognition, selectively disconnect power switches of the corresponding non-responsible consumers of electroe energies.

The essence of the emergency load limitation method in the power distribution network is illustrated by the drawings, in which Fig. 1 shows a simplified diagram of the implementation of the method as applied to the distribution network of the metropolitan area, Fig. 2 shows the timing diagrams of the commands for emergency limiting the non-responsible load transmitted through the power distribution network.

The implementation scheme of the method for the distribution network of the metropolitan area contains an electric power system 1, own source 2, power station 3, a power switch with a voltage of 10 (6) -20 kV 4 located at the transmitting end of the line, departing from power station 3, a transmitting device 5 (program switch) , metropolitan area 6, transformer substation 7 with a primary voltage of 6 or 10, or 20 kV and a secondary voltage of 0.4 kV, main switchgear 8 (GRU) 0.4 kV, receiving devices 9 (duration selectors), automatic electric switches 10.1 and 10.2 for voltage 0.4 kV, non-responsible consumers of electricity 11, responsible consumers of electricity 12. (For simplicity, the figure shows only one non-responsible and responsible consumer of electricity with related functional units).

The essence of the proposed method, providing disconnection of non-responsible consumers 11 of electricity with the transfer of appropriate commands deep into the distribution networks (including the voltage level of 0.4 kV) without the use of communication channels, consists in automatic short-term shutdown and subsequent inclusion of power switches 4 of the supply line from the power station 3 at a voltage level of 10 (6) -20 kV to create short-term interruptions of power supply (power) of a fixed duration on executive devices SHALL, including a low voltage level (typically - 0.4 kV) arranged directly at the non-critical power consumers 11 (controllable loads) and perceive this as a specific command for the implementation of selectively deactivating the corresponding non-critical consumer of electricity 11.

Non-responsible consumers of electricity include consumers of categories II and III in terms of reliability of power supply: non-responsible equipment, air conditioning, underfloor heating, jacuzzi (hydromassage), electric stoves, dishwashers, washing machines, water heaters, advertising, working lighting of stairwells of buildings, etc., which in the metropolitan areas mainly account for 90-95% of the load power.

The transmitting device 5, generating various commands in accordance with the number of the transmitted command, several times briefly turns off and turns on the power switch 4 of the supply line.

Reception devices 9 installed directly at disconnected non-responsible consumers 11 perceive commands in the form of voltage changes and selectively disconnect non-responsible 11 consumers of electricity. Responsible consumers 12 are not disconnected.

Timing diagrams of commands transmitted via a power distribution network for emergency limitation of non-responsible load are given as an example for three teams transmitted by a power distribution network for emergency limitation of non-responsible load, are time-pulse in nature and differ among themselves, in particular, the duration of the second pause between pulses of a fixed duration . The number of such commands and, therefore, the number of disconnected non-responsive consumers 11 can be significant.

Turning off and on under load a power switch 4 with a voltage of 10 (6) -20 kV at the transmitting end of the line departing from the power plant 3 for generating and transmitting commands does not reduce the resource of the power switch 4, since the total number of trips of the switch is not determining for the switches 4 4 in normal mode under load, and the number of short circuit shutdowns.

When implementing the command from the transmitting device 5 to shutdown, a short break is also created in the power supply of the responsible consumers 12 of electric power supplied by this line. But, given the short duration of the interruption in power supply (several tens of milliseconds), such outages for most consumers can be considered permissible. According to GOST 13109-97 “Requirements for the quality of electric energy in electric networks of general purpose”, the maximum allowable value of the duration of a voltage dip in electric networks with voltage up to 20 kV inclusive is 30 s.

In the presence of a significant synchronous load, the voltage on the power distributed line will decrease gradually and the receiving devices 9 may not work. In these cases, it is necessary to provide an additional start-up of the receiving devices 9 on the consumer side of the electric power 11 with a voltage of 0.4 kV according to the "OR" scheme from the frequency relay built into the receiving device 9 after the frequency decreases below 46 Hz. The receiving device 9 also produces a shutdown during an emergency voltage reduction.

Thus, the proposed method allows without additional communication channels to emergencyly limit the load in the power distribution network due to the selective disconnection of a dispersed set of non-responsible consumers of electricity. At the same time, power supply to responsible electricity consumers is reliably maintained.

Claims (1)

A method of emergency load limitation in a power distribution network, which includes an a priori division of electricity consumers into responsible and non-responsible, characterized in that in the event of an accident in the network, time-off code commands for shutting down are set for non-responsible consumers, a power plant is operating in emergency operation for an isolated load on a network section , in the switchgear located at the transmitting end of the line, departing from the allocated power station, in the event of an emergency and briefly turn off and turn on the circuit breakers and create interruptions of power supply of various fixed durations on the actuators of all electricity consumers connected to this line, in the switchgear of a lower voltage level, these interruptions of power supply are perceived as time-pulse code commands and selectively disconnect the circuit breakers of the corresponding non-responsible ones electricity consumers.

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