purchase & stores division - ISRO

voltage and frequency are subject to variation as per statutory limits governed by
Indian Electricity Rules 1956 with latest amendments in force.
DESIGN CRITERIA
4.1 The 11kV Switchgear shall be installed at the location shown in the SLD. The 11kV
distribution system, Vacuum Circuit Breaker shall be used to Control and isolate the
11kV / 433V Cast Resin dry type distribution transformers / HT Consumers
connected through 11kV grade underground cable at distribution center.
4.2 The Switchgear and component thereof shall be capable of withstanding the
mechanical and thermal stresses of short circuit listed in ratings and requirements
clause without any damage or deterioration of the materials.
4.3 For continuous operation at specified ratings temperature rise of the various
Switchgear components shall be limited to permissible values stipulated in the
relevant standard and / or this specification.
4.4 The equipment offered shall be suitable for continuous satisfactory operation as per
site condition specified elsewhere.
5.0 Fabrication:
Totally modular design concept.
Free standing, floor mounting and suitable for out-door installation.
The panel shall have easily removable and interchangeable sections.
Required service clearances shall be provided to carry out preventive and remedial
maintenance from front and rear side.
The panel shall be naturally convection-cooled & shall allow continuous full-load
operation, maintaining the temperatures within tolerance level of components.
Each bus bar compartment should have a barrier with 1.6 mm thick electro galvanized
coated / painted with fire resistance paint.
The degree of protection for the panel shall be IP 54 for VCB & IP 55 for LBS
6.0 GENERAL FINISH
The equipment should be totally enclosed, metal clad, vermin and dust proof suitable
for tropical climate use as detailed above. The body of the cubicle should be of
metalised and rust free.
6.1 Type of equipment
The equipment shall be compact, totally enclosed in as self contained self contained
self supporting compartment, mounted on base frame or channels. The assembly
shall be equipped with common power bus bar, load break Switches and Vacuum
circuit breaker as specified in specific requirement as above. All medium voltage
parts should be totally enclosed.
6.2 Bus bars:
a. Busbar material – Copper
b. The bus bars shall be Epoxy insulated High-purity electrolyte grade copper E-Cu 57
confirming to latest IS standard of 120 % rating of the switchgears.
Ele. Conductivity : 100% as per IAC Standard
Confirming to: DIN 1759, DIN 40 500 and relevant bus bar IS standard
Page 12 of 23