Creepage distance

The minimum clearance and creepage distances must be maintained for conductors as specified. 

Anti-loosening, anti-rotating type terminal arrangement with specified clearance and creepage distances... 

To contain the temperature of the electrical circuits within safe limits for a particular temperature class of the surroundings, the maximum current rating for a minimum size of a conductor is also stipulated in ICC 60079-1 I. The constructional requirements also stipulate the minimum clearances and creepage distances in air between the conducting parts of all the intrinsically safe L lectrical eirctiits. 

Special-purpose motors such as increased safety motors, flame-proof or explosion-proof motoi s must be checked for gaps, clearances and creepage distances of all the mating parts forming flame paths. The construction of these motors must follow lEC 60079 as noted in the list of standards. 

The clearance and creepage distances between the terminals and between each terminal and the ground. 

To comply with the rated insulation level, all the current-carrying components forming part of the assembly should have clearances and creepage distances according to their relevant standards whereas busbars and busbar connections must have the distances noted below. 

The clearances and creepage distances should be maintained as shown in Tables 28.4 and 28.5. These values can be reduced when ... 

This check may be carried out both at the works, after final assembly, and at the site after the installation before conducting routine tests or energizing the assembly. The ehecks can be carried out at a lower voltage to detect any shorting links or spanners left inadvertently on live terminals, weak insulation or insufficient clearance or creepage distances between the phases or phase to ground conduetors. In the ease of a defect the same must be rectified immediately. 

Table 15.1 Recommended values of minimum creepage distances for a VT or a CT...

Pollution level Minimum creepage distance between phase and ground mm per kV(r.m.s.) (phase to phase)... 

The rated frequency, insulation systems and the requirement of creepage distances will generally remain the same as for a voltage transformer (Section 15.4,1). For the remaining parameters, the following may be noted. 

These values are considered for an altitude of up to 2000 m for LT and 1000 m for HT systems. For higher altitudes to achieve the same level of dielectric strength, the values of clearances and creepage distances, as given in Tables 28.4 and 28.5, may be increased by at least 1 % for every 100 m rise in altitude. 

Table 28.S Creepage distances for enclosed indoor air insulated busbars as in BS 159 ...

Rated voltage e Minimum creepage distance to ground Minimum creepage distance between phases... 

The creepage distance between the opposing phases of the input (between the -I- and - dc and between the HI and H2 (or hot and neutral) must be 3.2mm minimum. 

Table 6.4 Creepage distances and distances through filling material...

Peak voltage Creepage distance CTI2 minimum Creepage distance Distance through V1 mm values under coating filling material... 

In addition, the reliability of an insulating material is strongly influenced by the pollution which may occur on its surface. So, creepage distances have to be increased for a higher pollution degree. 

Table 6.18 gives a survey of these relations according to IEC 60664-1 for normal industrial equipment compared with the specifications according to IEC 60079-7 and EN 50019 for increased safety - e Figure 6.39 shows creepage distances at a terminal block. 

In the high voltage range, the creepage distances are identical to those for pollution degree 3. It should be remembered that increased safety asks for IP 54 as an adequate ingress protection degree for the enclosure (with bare live parts inside). 

Table 6.18 Minimum creepage distances for electrical equipment subject to long-term stresses (the values given for IEC 60 664-1 are only a part of the standard s content)... 

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