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