TRANSFORMER TESTING - Voltage/Turn Ratio Test - Routine

 

EARTHING CONCEPTS

 EARTHING CONCEPTS 

1. TNC system 

2. TNC-S system 

3. TNS system 

4. TT system 

5. IT system 

IR VALUE FOR ELECTRICAL CABLE & WIRING

 

IR Value for Electrical cable and wiring:

• For insulation testing, we need to disconnect from panel or equipment and keep them isolated from power supply. The wiring and cables need to test for each other ( phase to phase ) with a ground ( E ) cable. The Insulated Power Cable Engineers Association (IPCEA) provides the formula to determine minimum insulation resistance values.
• R = K x Log 10 (D/d)
• R =IR Value in MΩs per 1000 feet (305 meters) of cable.
• K =Insulation material constant.( Varnished Cambric=2460, Thermoplastic Polyethlene=50000,Composite Polyethylene=30000)
  D =Outside diameter of conductor insulation for single conductor wire and cable
• ( D = d + 2c + 2b diameter of single conductor cable )
  d – Diameter of conductor
  c – Thickness of conductor insulation
  b – Thickness of jacket insulation

HV test on new XLPE cable (As per ETSA Standard)

Application	Test Voltage	Min IR Value
New cables – Sheath	1KV DC	100 MΩ
New cables – Insulation	10KV DC	1000 MΩ
After repairs – Sheath	1KV DC	10 MΩ
After repairs – Insulation	5KV DC	1000MΩ

11kV and 33kV Cables between Cores and Earth (As per ETSA Standard)

Application	Test Voltage	Min IR Value
11KV New cables – Sheath	5KV DC	1000 MΩ
11KV After repairs – Sheath	5KV DC	100 MΩ
33KV no TF’s connected	5KV DC	1000 MΩ
33KV with TF’s connected.	5KV DC	15MΩ

IR VALUE OF SUBMERSIBLE MOTOR

 IR Value of Submersible Motor:

IR Value of Submersible Motor
Motor Out off Well (Without Cable)	IR Value
New Motor	20 MΩ
A used motor which can be reinstalled	10 MΩ
Motor  Installed in Well (With Cable)
New Motor	2 MΩ
A used motor which can be reinstalled	0.5 MΩ

HR & Admin ISO Internal Audit 2021 Report in Amara Raja Infra Pvt Ltd

 

Damage of 33KV/415V Transformer HT Bush & HT cable kit due to Moisture in HT Enclosure box

Here I enclosed the damages caused by Moisture inside the HT cable box

REASONS FOR MOISTURE 

•  Improper installation of Gaskets
•  Improper tightness of Bolts and Nuts of Enclosure box 

This is a simple check if we are careless on this it causes the following major incidents in Transformer 

DAMAGE CAUSED DUE TO MOISTURE 

• Failure of cable kit due to moisture on kit which may cause flash over of cables 
• Failure of HT bush which may cause major oil leakage and flash over 
  

LIGHT COLOUR TEMPERATURE

Warm Light  (2000K-3000K):  Typically for ambient lighting in relaxation/leisure areas like Living Rooms, Hotel Lounges, Restaurants.

Neutral Light (3500-4500K): Typical for general purpose such as Offices, Lobbies, Classrooms, and Retail

Daylight White (5000-6000K): Typical for high task high visibility needs such as Workshops, Laboratories, Kitchens, and Manufacturing  

Cool White (5500-6500K): Typical for outdoor lighting such as street lights, parking lots, warehouses