| Customization: | Available |
|---|---|
| Application: | Construction, Overhead, Underground, Industrial, Power Station, Telecommunication |
| Voltage: | High Voltage Cable |
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Technical characteristics of 145 kV SF6 circuit breaker switches
1.1. Standards
Circuit breakers meet the requirements specified in EN 62271-1, EN 62271-100, EN 60273, and other relevant EN (IEC) standards.
1.2. General requirements
Circuit breakers is a "live-tank" type, for external installation, with SF6 gas for insulation and a medium for extinguishing the arc.The driving mechanism is motor-spring.
In order to maintain the stability of the system and reduce electrical, mechanical and thermal stress, the working times for switching off of the fault currents is as short as possible.
Apart from switching off short-circuit currents, the circuit breaker is able to perform other operations such as disconnecting the capacitors, transformers and power lines.
1.3. Technical Description
1.3.1. Circuit breaker poles
Circuit breakers use the "SF6 single-pressure" method to extinguish the arc.
The insulator is of porcelain.
The circuit breaker mechanically dimensioned to the short-circuit loads and tensile strengths of IX-level earthquakes by EMSC-98. The high voltage connections are made of aluminum with screw holes according to IEC standards.
The circuit breakers are designed for single-pole and three-pole quick re-start. The drive mechanism has the option of automatic re-start (APV) with cycle O -0.3 s - CO - 3 min - CO.
The circuit breakers are equipped with a temperature-compensated density gauge for indication of the gas pressure. The meter control the pressure of the gas in the chambers and provide alarm signaling and blocking at the following:
· First degree Alarm
· Second-level Blockage of Switch on / Switch off
Each density meter contains a pressure gauge, easily readable, preferably with a scale indicating the absolute pressure in MPa.Circuit breakers have a mechanically connected indication system that at any time gives clear and unambiguous information about the position of the main contacts.
The Circuit breakers have built-in protection against non-symmetry of poles (for a single-phase operated circuit breakers).
The Circuit breakers are designed so that it can be transported with a SF6 gas with transport pressure above the atmospheric, in order to avoid the vacuuming of the chamber during installation.
1.1.1. Drive mechanisms
The drive mechanism is placed in a cabinet made of metal plates and be resistant to a polluted atmosphere.
The cubicle meets the requirements for protection class IP 55 in accordance with IEC 60529.
The drive mechanism is motor-spring, with the possibility of mechanical and electrical shut-off and switch-on. The motor is maintenance free.
The driving mechanism has the following properties and equipment:
· Springs rolled up (charged- tensioned) with an electric motor, preferably of a universal type. The motor is protected by MCB with auxiliary signaling contacts. When the spring is charged, the end switch switch off the electric motor.
· A mechanical or electrical indication visible from the outside of the control cabinet will indicate when the spring is charged or discharged. The circuit breaker can never be switch on or switch off if the spring is discharged or insufficiently charged (tensioned).
· The drive mechanism is able to manually roll up (charge) the spring using the handle. When the handle is in use, the motor should be blocked (electrically).
· In each of the drive mechanisms of the circuit breaker, there has one coil for switch-on and two coils for switch-off. Each switch-off coil should be with separate circuits.
· Counter of operation - non-return type.
· Anti-pumping system
· Relays for blocking of all operations on the circuit breaker in case of a gas pressure drop at the blocking level.
· Signal switch with contacts, which will enable confidential operation of the switch and with sufficient number of contacts required by the user. The contacts of the signal switch are to be connected to the rails with regular clamps in the control cabinet.
· One heater always switched on, and one operated via a thermostat or through a humidity detector. Heaters should be protected with MCB with auxiliary contacts.
· Terminals (connection clamps) for connection of power and control cable. The connecting clamps are M4/6 type with 20% free clamps.
· The connections in the cabinet are from flexible copper conductors (wires) with the necessary cross-section which will withstand the currents flowing in the auxiliary, command and circuits of the electric motor. The conductors are marked at both ends in accordance with the marks given in the circuit diagrams.
1.1.2. Central control cabinet
In order to enable local three-pole control of a single-pole circuit breaker, a central control cabinet should be installed.
The central control cabinet shall contain (minimum) the following properties and equipment:
· Control panel with two selectable switches, one for local switching on - switching off and one with positions LOCAL - REMOTE - DISCONECTED. In the LOCAL position, the circuit breaker can be operated locally, but it will enable relay protection signals to switch off the circuit breaker.
· Terminals (connecting clamps) for connection of power and control cable and connection of the working mechanisms of the three poles. Connecting clamps should be M4/6 type with 20% free connecting clamps.
· "Non-symmetry of poles" should be controlled with time relays. The non-symmetry of the poles should execute the switch off of the circuit breaker and give an alarm signal.
· Single phase socket and inner illumination of the central cabinet.
· Heaters in the cabinet. One should be constantly switched on and the other should be controlled by a thermostat. Heaters must be powered by an automatic fuse with auxiliary signaling contacts.
· The connection between the central control cabinet and the working mechanisms of the poles must be with factory-prepared connectors, for external installation, for quick and reliable installation of the circuit breaker. Connectors should be provided for heavy duty and be as Harting connectors or equivalent to them.
1.1.3. Supporting construction
The poles in the three pole circuit breakers (for transformers bays) are installed on a common horizontal beam with two vertical supports, and the poles of the single-pole circuit breakers (for transmission line bays) are installed on separate vertical supports or on a common beam with two vertical supports. The construction is made of hot galvanized steel. The thickness of the galvanized layer is in accordance with EN-ISO 1461: 1999, table NA.1, Fe / Zn115.
The supporting construction of the single-pole circuit breakers provides lugs for carrying of the communication cables between the drive mechanisms and the central control cabinet.
The supporting construction has sufficient height to ensure the safety of the personnel in the plant when the circuit breaker is switched on.
All elements for connection (screws, nuts, pads, etc.) are hot dip galvanized.
Grounding points are prepared on supporting construction for connection to the grounding in the substation.
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