Earthing link boxes for medium and high voltage up to 500kV
We have an extensive technical engineering background in the development and production of grounding boxes for medium and high voltage underground insulated cable systems. In addition to standard enclosures, we can offer enclosures to suit customer requirements.
At RH we are specialists in the design and supply of earthing link boxes for protection of buried cables up to 500 Kv.
With more than 250 different designs at present, we cover all our customers’ needs whatever their network configuration and environmental environment. We have software for project calculations.
Manufactured using high quality production processes, they guarantee a supply that complies with the most demanding electrical, mechanical, sealing and corrosion standards.
All our enclosures are individually tested before being delivered to our customers.
They are designed according to the customer’s needs, with or without limiters.
Electrically, it is one of the most important integral accessories of any insulated underground cable jointing system for medium and high voltage networks.
The system is designed in such a way that the cable screens are bonded and earthed directly or through an SVL limiter in such a way as to eliminate or reduce currents flowing through the screens.
Grounding boxes are used to make good use of cable joints or splices, as well as at terminations to provide easy access in case of testing using the screens, and to limit possible damage to cable sheaths. Earthing boxes are an essential part of the earthing and protection system to improve current carrying capacity and human protection.
1- Single Bonding
Single bonding is the simplest bonding and consists of arranging the three phases so that they are connected to earth at only one point along their length. At all other points, a screen voltage to earth will appear which will be a maximum value at the furthest point of the earth bond.
The screen must be properly isolated from earth. As long as the screen circuit is open (except when a voltage limiter is present) the current will flow longitudinally and smoothly avoiding possible damage to the sheath or losses.
2- Cross bonding and screen transposition
It essentially consists of cross-sectioning the cable screens to minimise or neutralise possible induced stresses in three consecutive sections.