System Commissioning of BPDB Lalmonirhat 33/11kV Substation, Package-04

Novelty was selected by CEEC to construct new 33/11KV 2X16/20 MVA AIS Substation, at Lalmonirhat, Rangpur Zone of BPDB. The objective of this project was to reach power to the people in a timely manner.

Here we have installed 16/20MVA 2 nos. Power Transformer, and test those transformers turn ratio, winding resistance, insulation resistance, magnetizing current, bushing CT ratio, Ten Delta and oil break down voltage and others by using Omicron CPC 100, CP TD 12 & Kyoritsu high voltage insulation resistance tester. At this substation we also install outdoor 33kV instrument transformers, LA, Insulators, Isolators ETC. All the instrument transformers ratio and insulation Resistance tested by using CPC 100, CT Analyzer & High voltage insulation resistance tester. We have also installed 33kV Outdoor VCB and indoor Control panels and also tested those by Megger breaker analyzer, CPC 100 for contact resistance test, High voltage insulation resistance tester for IR Test & test relay's by CMC 356. We also install testing and commissioning 11kV incoming and outgoing indoor type VCB panels and tested those by Megger breaker analyzer, CPC 100 for contact resistance test, High voltage insulation resistance tester for IR Test & test relay's by CMC 356. We have also installed, test and commissioned earthing system in this substation.

Air Insulated Substation (AIS) or Outdoor Substations have all switchgear equipment, busbars and other switchyard equipment installed outside open to atmosphere. In earlier days for any voltage ratings AIS or outdoor substation is employed.

Indoor Substation type is only employed in places where high pollution or saline environment exists. Indoor substations are of two types

• Substation with conventional switchgear equipment enclosed in big building. Size of switchyard is similar to AIS Substation.
• Substation with SF6 enclosed modules (Gas Insulated Substation) in building which takes about 10% of the total AIS substation space

Because of excellent properties of SF6 gas such as high dielectric strength, high electronegativity, for EHV substations more than 230kV now a days Indoor Gas Insulated Substations (GIS) are employed in place of AIS substations. However the cost of GIS indoor substation is higher compared to AIS substation but it has some benefits which includes high reliability, less space requirement and less maintenance.

This type of substation arrangement is best suited for low voltage rating substations (step down substations) and for those substations where there is ample amount of space available for commissioning the equipment of the substation. The construction work required is comparatively less to indoor switch yard and the cost of switchgear installation is also low.

In future the extension of the substation installation is easier. The time required for the erection of air insulated substation is less compared to indoor substation. All the equipment in AIS switch yard is within view and therefore the fault location is easier and related repairing work is also easy

There is practically no danger of the fault which appears at one point being propagated to another point for the substation installation because the equipment of the adjoining connections can be spaced liberally without any appreciable increase in the cost