What is the maximum ZS permitted by BS7671?
The 1.37 ohms value is the 100% max Zs value which should be recorded on the test certificate.
What is a BS88 fuse used for?
A BS88 fuse contains a sacrificial link that breaks during an overload or short circuit scenario to protect the rest of the electrical system. BS88 fuses are used in low voltage industrial and general-purpose applications and meet the requirements of BS88 and IEC60269.
What type of fuse is BS88?
TIA BS88, IEC269 Industrial Fuse Links Offset Bolted Tags 550V ac This range of Q1 fusing factor general purpose (gG) fuse links has a breaking capacity of 80kA ac and 40kA dc where applicable.
How do you find Zs of a circuit?
Therefore, where reliable measured values are available for the external earth loop impedance (Ze) and for the loop resistance of the line and protective conductors (R₁ + R₂) of the circuit, it is permissible to derive the loop impedance of a circuit by using the following formula: Zs = Ze + (R₁ + R₂).
What is Zs in electrical terms?
Zs represent earth fault loop impedance and consists of Ze and (R1+R2). These are measurements of the fault current from the supply transformer to the building. It covers the entire electrical cycle. If Zs are too high, not enough fault current can flow and the MCB may not trip at all.
What type of fuse is BS88 2?
The fuse complies with standard EN 60269-2 section II and standard BS 88 part 2. This fuse range insures an excellent current limi- tation for all overloads on a large range of appli- cations. Their size cannot allow exchange by other fuses of higher rating in their range.
How does a BS88 2 fuse work?
(Inside the BS88 fuse body is the fuse wire/wires which are surrounded by sand. The fuse clears the fault once the wire/wires are melted inside the sand). So the fuse is melted by energy which is the I2T number you are referencing.
Are gG fuses Motor rated?
As a first approximation – “gG” are general purpose fuses (i.e. normal ones) and “aM” are “motor” fuses (i.e. ones intended to withstand the startup surges from motors or other similar equipment) – typically providing a higher rated fusewire element within a lower rated cartridge (e.g. 20M25) and often only used to …
What does F mean on a fuse?
T = slow burn fuse. F = fast acting fuse. TT = very slow burn fuse. FF = very fast acting fuse.
What is the maximum value of ZS for a fuse?
Table 1 – Maximum measured values of Zs for fuses. Note: Values of Zs for disconnection times other than 0.4 s or 5 s shown may be required by BS 7671 . For example, 0.2 s may be required for a 230 V final circuit not exceeding 32 A in a TT system (Table 41.1 refers).
What is a bs88 fuse?
The first definition of British Standard 88 was limited to the fuses of that time. It was generally redefined in 1931, giving the time, temperature and other definition how the fuselink has to function. Since this time BS88 has several time be revised. BS 88 fuses dated from 1919 could be still in use even today.
What is an ASTA 20 fuse?
Approval Asta 20 Certified • The fuse complies with standard EN 60269-2 section II and standard BS 88 part 2. •These fuses are designed for : – “General purpose use” protection (gG type) – motor protection (gM type) •This fuse range insures an excellent current limi- tation for all overloads on a large range of appli- cations.
What is the British standard for fuses?
The first British specification that defined the performance requirements of fuses for BS 88 was introduced 1919. In the time before exists a wide variety of fuses, but without national, British Standard. The first definition of British Standard 88 was limited to the fuses of that time.