An example of new solutions can be any modern field of double-member switchgear in air insulation. The number of operating apparatuses has been reduced (there are only two: a circuit breaker or a disconnector and an earthing switch), and the whole is connected by a system of mechanical and electrical interlocks, so that an employee operating the apparatuses cannot perform a forbidden operation (e.g. closing the earthing switch while the circuit breaker is closed in the “operation” position).
It is possible to use an extension member with a switch or contactor, instead of a stationary apparatus.
It is possible to use fixed members for pull-out switches. The members are available in two versions:
– fully enclosed and shielded cassette closed from the front with a door- fully enclosed and shielded cassette closed from the front with a door
– support frame (consisting only of a back plate with insulation grommets and bottom guides for the extension member.- Support frame (consisting only of a back plate with insulation grommets and bottom guides for the extension member.
The issue of “retrofitting” MV switchgear is one of the most current topics in the power industry. Every year, groups of users face the problem of using old switchgear, and everyone is faced with a decision: replacing apparatus or buying new switchgear.
We are confident that with the proposal presented, the existing alternative of solutions will expand, so that everyone will be able to better match an individual solution to their own technical and economic conditions.
The use of a cassette or support frame, in addition to increasing the reliability of the field, also brings additional benefits:
• Protects the operator from performing an incorrect operation (cannot enter and leave the field with the switch closed without first closing the earthing switch cannot move the earthing extension from the “work” position to the “test” position, cannot close the earthing switch before opening the switch.
• The structures are equipped with curtains of isolation grommets, i.e., when they are closed and locked, the staff cannot touch the fixed contacts in the grommets.
• extending the extension member to the “test” position and covering the isolation grommets with curtains allows the operator to see that there is a visible isolation break in the circuit on the supply side, as well as on the drain side; the extension member plays the role of two disconnects in the old system.
• any necessary apparatus can be installed on the extension member: vacuum circuit breaker, SF gas switch or contactor.
• in the event that in the future the user decides to buy a modern two-member hooded switchgear, he can use his existing extension apparatus without modifications.
• An additional advantage of cassettes and support frames is the speed of their installation in the field. This significantly reduces the time required to work on a single field in case you decide to replace all fixed apparatuses with new ones in the traditional way – “one for one”.
|Rated voltage||7,2; 12; 17,5 [kV]|
|Rated current||630; 1250; 1600; 2000; 2500; 3150 [A]|
|Rated short-term withstand current||20; 31,5 [kA/3s]|
|Lightning surge test voltage||125 kV|
|Rated continuous current||630 A|
|Rated withstand current||16 kA|
|Rated peak withstand current||40 kA|
Compliance with standards
High-voltage switchgear and controlgear – Part 1: Common provisions.
High-voltage switchgear and controlgear. Part 200: A.C. switchgear in metal sheaths for rated voltages above 1 kV up to 52 kV.