ARTICLE
Consider this when planning high voltage switchgear installations
Planning high voltage switchgear
The following three criteria must be considered when planning high voltage switchgear installations :
1 . Voltage levels 2 . Plant concept and configuration 3 . Dimensioning 1 . Voltage levels
High voltage installations are primarily for power transmission , but they are also used for distribution and for coupling power supplies in three-phase and HVDC systems . Factors determining their use include : network configuration , voltage , power , distance , environmental considerations and type of consumer
HV Installations Voltage level
Distribution and urban networks > 52 – 245 kV
Industrial centres > 52 – 245 kV
Power plants and transformer stations > 52 – 800 kV
Transmission and grid networks 245 – 800 kV
HVDC transmission and system interties > 300 kV
Railway substations 123 – 245 kV
2 . Plant concept and configuration
The circuitry of an installation is specified in the single-phase block diagram as the basis for all further planning stages . Table 1 shows the advantages and disadvantages of some major station concepts .
The availability of a switching station is determined mainly by :
1 . Circuit configuration , i . e . the number of possibilities of linking the network nodes via circuit breakers and isolators , in other words the amount of current path redundancy ,
2 . Reliability / failure rate of the principal components such as circuit breakers , isolators and busbars , 3 . Maintenance intervals and repair times for the principal components . Table 1 – Choice of plant concept and measures taken in relation to given boundary conditions
Concept configuration |
Advantages |
Disadvantages |
Single busbar |
1 . least cost |
1 . BB fault causes complete station outage 2 . maintenance difficult 3 . no station extensions without disconnecting the installation 4 . for use only where loads can be disconnected or supplied from elsewhere |
Single busbar with bypass |
1 . low cost |
1 . extra breaker for bypass tie |
2 . each breaker accessible for maintenance without disconnecting
By Edvard Csanyi Editor-In-Chief and electrical engineer at EEP http :// electrical-engineering-portal . com
2 . BB fault or any breaker fault causes complete station outage
Double busbar with one circuit breaker per branch
1 . high changeover flexibility with two busbars of equal merit
2 . each busbar can be isolated for maintenance
3 . each branch can be connected to each bus with tie breaker and BB isolator without interruption
1 . extra breaker for coupling
2 . BB protection disconnects all branches connected with the faulty bus
3 . fault at branch breaker disconnects all branches on the affected busbar
4 . fault at tie breaker causes complete station outage
22 Global MDA Journal may 2018