Automatic regulation of excitation, voltage and reactive power

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 3. Protection and automation

Automation and telemechanics. Automatic regulation of excitation, voltage and reactive power

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Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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3.3.51. Devices for automatic control of excitation, voltage and reactive power are designed for:

maintaining voltage in the electrical system and at electrical receivers according to the specified characteristics during normal operation of the electric power system;
reactive load distribution between reactive power sources according to a given law;
increasing the static and dynamic stability of electrical systems and damping oscillations in transient conditions.

3.3.52. Synchronous machines (generators, compensators, electric motors) must be equipped with automatic control devices. Automatic excitation controllers must comply with the requirements of GOST for excitation systems and technical specifications for equipment for excitation systems.

For generators and synchronous compensators with a power of less than 2,5 MW, with the exception of generators of power plants operating in isolation or in a low-power power system, it is allowed to use only relay forcing excitation devices. Synchronous motors shall be equipped with automatic control devices in accordance with 5.3.12 and 5.3.13.

3.3.53. The high reliability of the power supply of the AVR and other devices of the excitation system from voltage transformers, as well as the high reliability of the corresponding circuits, must be ensured.

When connecting the AVR to a voltage transformer with fuses on the primary side:

ARV and other devices of the excitation system, the loss of power of which can lead to an overload or an unacceptable decrease in the excitation of the machine, must be connected to their secondary outputs without fuses and automatic switches;
the relay forcing device must be designed in such a way that it excludes the possibility of its false operation if one of the fuses on the primary side of the voltage transformers blows.

When connecting the AVR to a voltage transformer that does not have fuses on the primary side:

ARV and other devices of the excitation system must be connected to their secondary outputs through automatic switches;
Measures must be taken to use the auxiliary contacts of the circuit breaker to prevent overloading or an unacceptable decrease in the excitation of the machine in the event of the circuit breaker being turned off.

As a rule, other devices and devices should not be connected to voltage transformers to which ARV and other devices of the excitation system are connected. In some cases, it is allowed to connect these devices and devices through separate circuit breakers or fuses.

3.3.54. The AVR devices of hydro generators must be designed so that in the event of a load shedding with a good speed controller, the operation of the overvoltage protection is excluded. If necessary, the ARV device can be supplemented with a fast-acting de-excitation relay device.

3.3.55. The scheme of the relay forcing excitation device should provide for the possibility of transferring its action to the backup exciter when it replaces the main exciter.

3.3.56. Excitation compounding devices must be connected to the current transformers on the output side of the generator or synchronous compensator (busbar side).

3.3.57. For synchronous generators and compensators with direct cooling, generators with a capacity of 15 MW or more and compensators with a capacity of 15 MVAr or more, power plants and substations without constant personnel on duty in the control room, automatic overload limitation with a time delay depending on the multiplicity of overload must be provided.

Before mastering the serial production of devices for automatic overload limitation with a dependent time delay for machines with a capacity of up to 200 MW (MVAr), it is allowed to install limiting devices with a time-independent characteristic.

The automatic overload limiting device must not prevent the forcing of excitation during the time that is allowed for the corresponding design of the machine.

3.3.58. For generators with a capacity of 100 MW or more and for compensators with a capacity of 100 MVAr or more, high-speed excitation systems with a strong action AEC should be installed.

In some cases, determined by the operating conditions of the power plant in the power system, it is allowed to install a different type of ARV, as well as slow-acting excitation systems.

3.3.59. The excitation system and AVR devices must provide stable regulation in the range from the smallest allowable to the highest allowable value of the excitation current. For synchronous compensators with a non-reversible excitation system, regulation should be provided starting from the value of the rotor current, which is practically equal to zero, and for compensators with a reversible excitation system, from the highest allowable value of negative excitation current.

For machines operating in a block with transformers, the possibility of current compensation for voltage loss in the transformer must be provided.

3.3.60. Generators with a capacity of 2,5 MW or more of hydro and thermal power plants with four or more units must be equipped with plant-wide automated control systems for technological processes or (in their absence) group excitation control systems. These systems on generators of thermal power plants are recommended to be performed depending on the scheme, mode and power of the power plant.

3.3.61. Transformers with on-load tap-changers of distribution substations and auxiliary needs of power plants, as well as linear regulators of distribution substations for maintaining or a given voltage change, must be equipped with an automatic transformation ratio control system. If necessary, automatic regulators must provide built-in voltage regulation.

Substations where parallel operation of transformers (autotransformers) with automatic regulation of the transformation ratio is provided, must be equipped with a general substation automated process control system or a group regulation system that excludes the occurrence of unacceptable circulating currents between transformers.

3.3.62. Condenser units must be equipped with automatic control devices in accordance with Ch. 5.6.

See other articles Section Rules for the installation of electrical installations (PUE).

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