Day: 5 February 2023

Consumer Unit

Atype of single-phase board for the control and distribution of electrical energy, principally in domestic premises. In the ProDesign software,a consumer unit (CU) can be split into three sections,each with different types of residual current protection.

Competent person

Aperson who possesses sufficient technical knowledge, relevant practical skills and experience for the nature of the electrical work undertaken and is able at all times to prevent danger and,where appropriate, injury to themselves and others.

Circuit Protective Conductor (CPC)

Acircuit protective conductor (CPC) connects exposed-conductive-parts* of equipment to themain earthing terminal. *Conductive part of equipment,which can be touched and which is not normally live,but which can become live when basic insulation fails.

Harmonic rating factor (Ch)

Ch Rating factor used for calculating theminimum required cable size in the presence of harmonic currents.See BS7671:2018,Appendix 4, section 5.5.

Grouping rating factor (Cg)

Grouping rating factor used for calculatingminimum required cable size. For cables installed in air, values for this factor are given BS7671:2018,Tables4C1,4C4,4C6.For ground installations, values are given in Table4C2. Grouping a circuit with others will result in a lower rating factor Cg. Thismay result in an increased cable size.

Depth of lay rating Factor (Cd)

The rating factor Cd is applied to cable sizing calculations for cable installed in the ground. Its value varies according to the depth of lay installed. See BS7671:2018,Table4B4. Indicates the depth of installation for cables installed in the ground. The rating factor Cd is applied in cable sizing calculations to account for different installation depths.For […]

Ground rating factor (Cc)

The rating factor Cc = 0.9 is applied to cable sizing calculations for cables installed in the ground (Installation Methods 70 to 73). See BS7671:2018,Appendix 4,Sections3,4 and 5.1.1.

Back-up Protection

Circuit-breaker manufacturers publish tables showing combinations of pairs of circuitbreakers, one upstream,one downstream,where the downstream device can be used at a location where the prospective fault current (Ipf) is higher than its breaking capacity (Icu). The Icu of the upstream devicemust equal or exceed Ipf at its point of installation.

Cable k2s2

k2s2 its an Energy withstand of cable in A2s. For example,a cable with a withstand of 12 x 104 A2s, can sustain without permanentdamage,a fault current of 1,000 A for a time of 0.12 s (1,0002 x 0.12 = 12 x 104 A2s).

Ambient temperature rating factor (Ca)

Ambient temperature rating factor used for calculating theminimum required cable size. For cables installed in air, values for this factor are given in BS7671:2018 Table4B1.For ground installations, values are given in Table4B2. Elevating the ambient temperature will result in a lower rating factor Ca.This may result in an increased cable size.

Breaking capacity

Diagram comparing coordination failure and selective coordination between protective devices in an electrical system. The top section shows a 32Amp circuit tripping a 63Amp breaker, causing upstream devices rated 125Amp and 160Amp to disconnect unnecessarily. The bottom section demonstrates selective coordination, where a 125Amp device isolates the fault without affecting upstream devices rated 250Amp and 600Amp.

IWE-S1-IWE- E8_Breaking Capacity of MCCB What is Breaking Capacity (kA) Breaking capacity, often referred to as short-circuit breaking capacity, is one of the most critical specifications of a protective device. Regardless whether its Fuse, Miniature Circuit Breaker (MCB) or  Molded Case Circuit Breaker (MCCB). This rating determines the maximum fault current the device can safely […]

Basic protection

Protection against electric shock under fault-free conditions;use of barriers,placing out of reach,and so forth.

Ambient temperature

The temperature of the free air surrounding a cable,or in the case of cables installed in the ground, the temperature of the surrounding soil.For an enclosed method such as ‘In conduit’ this will be the temperature of the air surrounding the conduit, not the temperature inside it.

Adiabatic

Adiabatic checks are required to determine whether conductorsmight be damaged by the thermal effects resulting from the level of calculated fault conditions.