Earth continuity cable

Sheath voltage limiter (SVL) ------Earth continuity cable (ECC)... 

A key factor in the design and choice of earth continuity conductors, e.g. cable armouring, bonding straps, and fault current protective devices is the earth loop impedance . This is especially the case for solidly earthed low voltage systems, whether they be three-phase, single-phase or even direct current systems. 

The cable is terminated with a simple gland which compresses a compression ring onto the steel wire armouring to provide the earth continuity between the switchgear and the cable. 

It is particularly important to check that the plug tops and cables of handheld electrically powered tools and extension leads are in good condition. Damaged plug tops and cables must be repaired before you use them. All electrical power tools of 110 V and 230V must be inspected and tested with a portable appliance tester (PAT) in accordance with the company s procedures, but probably at least once each year. PAT testing tests the quality of the insulation resistance and the earth continuity. Inspection checks the condition of the plug top, fuse and lead. 

Flexible metallic conduit should have a non-metallic inner sheath or be suitably designed so that movement cannot cause abrasion of the cables. Flexible metallic conduit is not a suitable protective conductor. A flexible cable conductor should be used for this purpose to ensure earth continuity between the fixed conduit and apparatus, and the flexible conduit joints should be earth bonded at both ends. 

Cable tray routes as per drawing Cable tray suppoits adequate and secure Cable tray assembled and secured correctly Cable ttay earthing as per specification Cable tray earth continuity checks satisfactory Earth cables/bonds securely terminated Cables securely banded/shrouded Correct cable glands fitted Junction boxes and covers securely fitted Flameproof equipment fitted as per specification Lighting fittings correctly erected and secure Distribution boards installed and connected as per drawings... 

It is essential that portable apparatus is properly maintained, with the earth core of the flexible cable and associated earth connections being tested regularly by a competent person using a substantial current (special test sets are available) to ensure continuity and strength of the earthing. 

Exposed steelwork used in the construction of the building should be continuously joined by welding or by jumper cables welded to bridge individual components. The whole should be earthed to a suitable ground mat or ground rods. Day tanks for organic feedstocks or products, equipment frames and the ESP must be similarly earthed. 

All fixed distribution cables carrying 400V or 230V must be protected with a metal sheath and/or armour which is continuous, effectively earthed and protected against corrosion. The HSE strongly recommend that any existing or new permanent fixed supply should not be used to supply contractors equipment during the construction work. Any movable plant such as lifts or hoists should be supplied by armoured cable. 

The IT supply system is the same as a TT system (a TT installation is one in which the earth is derived from a local earth electrode rather than from the suppher s supply cable - see Chapter 10) but either without a source earth or with earthing through a high impedance. It is not legal for public supplies but may be used in private installations. The system is monitored to provide visual or audible warning of an earth fault. The applications include continuous processing plants and medical intensive care apparatus where the supply needs to be maintained even if an earth fault should occur. It is occasionally used to supply test facilities as it affords protection against direct shocks. As described for electrical separation , which is a form of IT system, a direct shock hazard arises only if there is an earth fault, and an... 

Check the position of the meter. The Electricity Supply Regulations require it to be installed in the consumer s premises unless it is more reasonable for it to be located elsewhere, in which case it should be accessible to the consumer. This is more likely to occur in blocks of flats and housing in multiple occupation. In such premises the supply authority may bring in only one service cable on to a busbar and then feed each tenant via cables in conduit or sometimes in MIMS cable. The latter is not a good choice because the insulation is hygroscopic and if the end seals fail, the cable can break down. It may also fail if subject to HV transients, so such cables should be fitted with suppressors. If the conduit or sheath of the MIMS cable is used as the earthing conductor, check that the connections are satisfactory and of low resistance and any joints in the conduit provide adequate continuity. 

The pH probe may be coimected to a double-screened cable, with the outer screening earthed at the amplifier and the inner screening coimected to the reference electrode. The probe may be programmed to be inserted and retracted every minute to allow continuous pH readings to be made. However, the probe may need to remain in the bath for about 10s each time to establish the equilibrium prior to recording values. 

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