MCR-25/110: Three-Phase MCR System (Patented)

FIELD OF APPLICATION:

MCRs of this type are used in electric distribution networks of 6, 10, 35, and 110 kV rating.

Connected to busbars of 110 kV substations with circuit breaker and disconnector.

PURPOSE

To prevent emergency network over-voltage and keep it within 1.0 ú 2.5 percent of rated network voltage at point of connection.

To lower by 15 ú 20 percent power transmission and distribution losses due to minimization of reactive power transfer through the network.

To reduce by dozens of times the intensity of operating the switching equipment in voltage control circuits.

COMPLETE EQUIPMENT

As shown in the schematic diagram below the MCR 25/110 consists of the following parts:

• Electromagnetic portion (1), placed in a tank.
• A 160kW/10kV transformer with built-in thyristor 120V/800A AC/DC converter.
• MCR 25/110 control, regulation and protection system (3).

MAIN TECHNICAL DATA

WINDING CONNECTIONS

Phases of network winding of MCR 25/110 reactor are Y-connected and grounded.

MCR 25/110 control windings of phases are delta-connected.

Transformers with built-in thyristor converters are connected to equipotential points of reactor control windings.

MCR 25/110 control systems are connected to control inputs of transformers with built-in thyristor converters, to current transformers (5) at the MCR phases, and to substation voltage transformers (4) at 110 kV busbars.

OPERATING CONDITIONS

These MCRs are designed for outdoor operation in moderate climate with elevation up to 1000 m above sea level. Each module is placed in an oil-immersion tank with natural cooling. The main parameters of the module are as follows:

The associated transformer with built-in thyristor converter is also designed for outdoor operation. It is placed in an oil-immersion tank for natural cooling.

Control, adjustment, and monitoring system for indoor installation on a substation switchboard panel:

PRINCIPLES OF OPERATION

As shown in the figure above, voltage stabilization at a 110 kV substation is performed in automatic mode by a smooth change of the consumed power of reactor (1) in accordance with a mismatch signal generated by control system (3). The consumed current of reactor (1) is changed as result of direct current produced by a thyristor converter (2) magnetizing its magnetic system.

When the voltage increases to 2.5% above the given pre-set value, the consumed power of reactor (1) is smoothly changed within the range of 0.25 to 25 MVA with an equivalent time constant not exceeding 1 second.

Compensation of excess charge power of transmission lines is carried out automatically according to the pre-set, operator-fixed value of converter (2)'s saturation angle adjustment. The MCR's idle current can be preset from 2.5 to 114 A.

EFFICIENCY OF APPLICATION

Design, weight, dimension, and maintenance of the MCR 25/110 are similar to general-purpose, two-winding power transformers of the same power and voltage class. This results in device effectiveness and reliability of operation.

Operation of the MCR 25/110 does not require specific training of maintenance personnel.

Time of recovery of outlay for MCR 25/110 is 1.5-2 years.

TOTAL COST OF OWNERSHIP (TCO)

As a percentage of ex-works price TCO is as follows:

In other words, the TCO of an MCR is similar to that of a transformer of the same class.

MEAN TIME BETWEEN FAILURE (MTBF)

CERC guarantees its MCR's for a lifetime of not less than 25 years, with first major maintenance guaranteed not to occur within 12 years.

Each phase of the reactor, its grounding filter and current-distortion corrector (an LC filter) are guaranteed for a minimum of 3 years.

The power control system, including the transformer with its built-in thyristor subsystem is guaranteed for one year. The average practical time to failure of smaller MCR's is 5 years.