Construction of substation 220 kV Lafarge. Volume 2. Relay protection and automation, страница 2

Diagram of the connection with the power grid of OAO «UES FGC» provides power supply of energy receivers of ООО «Lafarge GEO» with the quantity of 55.5 megawatt and has the 2nd category of reliability of power supply.

1.2. The substation will has two three-phase three windings 220/35/6,6 kV with the power of 63 MVA.

1.3. The diagram of the switchgear 220 kV is «Two blocks with circuit breakers and not automated bridge on the side of the line feeders ».

Nominal current of the SF6 circuit breakers of the line feeders is 4000 А, maximum breaking current – 50 kА. Each circuit breaker have two opening electromagnets.

Each circuit of the circuit breaker has current transformer with three secondary windings (accuracy class 5Р). Secondary current of current transformers – 1 А.

Each line feeder 220 kV has voltage transformer with three secondary windings.

1.4. According to the requirements of this project, substation Lafarge will has two banks of accumulators. Voltage of the operating direct current – 110 V.

1.5. Connection of the high-voltage lines 220 kV of substation Lafarge with switchgears of the opposite substations.

The feeder lines of the substation Stany (the diagram of the switchgear 220 kV is «two working busbars») connected  through one circuit breaker. The circuit of the circuit breaker has current transformer with five secondary windings, three of which have accuracy class 10Р, others are 0,2 and 0,2S. At the moment, protections of the line feeders are using two secondary windings of the current transformers. Their nominal current is 1 А. Voltage of the operating direct current – 220 V.

2. General provisions of implementation of relay protection and automatics

2.1. According to requirements specification we develop relay protection and automation solutions of the substation Lafarge and adjoin grid with usage of microprocessor-based relays. The usage of such type of relays is a progressive step and it gives some important advantages, such as:

- possibility of realization several functions of relay protection and automation in one device, and also some additional functions, such as oscillography, registration of the events, detection of the fault location;

- realization of new guidelines and improved features;

- comfort during adjustment and exploitation;

- wide system of self-test;

- possibility of integration relay protection and automation devices with process control system;

- possibility of the usage the interchange of logical signals between devices for realization relay protection functions with fiber-optic digital communication channels, replacing the traditional cable connection which is out of control;

- low values ​​of power consumption.

We recommend microprocessor-based terminals which have attestation opinion, approved by OAO "UES FGC".

2.2. The complexes of relay protection should meet the requirements of current RF standards and ensure speed, reliability, selectivity and sensitivity.

2.3. Increased reliability of relay protection and automation is provided with near back-up:

- mounting two kits of protection;

- usage of breaker failure protection;

- division of protection kits by usage of separate operating circuits (~ ; =) and “open/close” circuits, reservation of this circuits;

- placement of devices, reserving each other, in different cubicles.

2.3.1. Division of protection kits by usage of separate operating circuits means that protection kits have power supply from different secondary windings of current transformer.

Current operating circuits must be made with separate screened cables, which are laid, if it is possible, in different cable trays.

2.3.2. Division (reservation) by usage of separate operating circuits must be carried out according to PUE (Rules for Electrical) recommendations.

2.3.3. Main and back up protections of the feeder lines are connected with assemblies, powered by separate banks of accumulators, through circuit breakers.

Reservation of the power supply must be ensured by diagram of the electrical connections of the direct current box and the diagram of direct current networks organization.