10 - Electrical Safety & Hazards (EN50110-1)

Question 1

The ability to explain the definition of Low Voltage in accordance with EN50110-1 and WTSR.

Answer 1

What is HV and when is it LV?
LV does not exceed 1000VAC or 1500VDC. HV is everything exceeding this.

How is this applied on the WTG?
On Offshore WTG the switchgear and transformer are located at the bottom of the tower in separate enclosures. From the transformer down to the switch gear, HV rules apply, otherwise it is WTSR.

What different voltages can you expect in the WTG?
- Generator – 710VAC
- MSI – 1150VDC +/-
- LSI – 640VDC
The LSI voltage then splits between the transformer and IPS transformer.
- Transformer – 33/66KV
- IPS Transformer – 3 Phase 400/240VAC
The voltages produced from the IPS transformer supply various AC/DC cabinets throughout the WTG and converted into the following voltages…
- AC Cabinets – 110VAC, 230VAC, 400VAC
- DC Cabinets – 24VDC, 110VDC, 230VDC, 400VDC, 560VDC
- Main Backup Batteries – 48VDC (4x8 packs of batteries (32))

Question 2

The ability to explain or demonstrate the process for isolation and proven dead on the different types of circuits in the WTG.

Answer 2

• Ensure the testing equipment is approved according to the MAN Approved List of CHE Tools and Equipment
• Ensure the equipment is in good working condition, is calibrated and in date
• Using a proving unit, test the testing equipment
• Carry out a test of circuit as defined in the AWP
• Carry out a post use test of the testing equipment with the same proving unit used initially
  The process must be carried out for each individual isolation, using the proving unit between each of these individual tests

Question 3

The ability to explain the between different electrical protection equipment such as MCCBs, RCDs, thermal protection relays and contactors.

Answer 3

MCCB – Also Fuses
- Designed to trip/cut off on overcurrent i.e. pulling too much load/amps
- Protection of equipment
- Operated by thermal or magnetic means (Usually both)
RCD
- Trips upon earth leakage (normally >30mA)
- Protection for persons
- Operated by thermal or magnetic means (Usually both)
Thermal Overload Relays/Contactors
- Protects motors from over-current caused by fault, overload, stall, or long start-up times.
- Often adjustable to suit specific motor characteristics
- Mounted to motor contactor

Question 4

The ability to explain the different types of stored electrical energy in the WTG.

Answer 4

• PCM3 DC Backup batteries

- MSI capacitors

Question 5

The ability to explain what type of PPE is to be used when working on or nearby electrical systems.

Answer 5

Information can be found in QSE-INS Working in Live Electrical Area PPE Standard and Specification
Insulating Gloves
Pre-Use inspection
- Visually inspect both gloves and subject them to an air test, no air should escape from either gloves.
ELV
Testing for dead
- Safety Glasses, Safety footwear, Class 1: Arc/Flame resistant clothing
LV
Testing for dead
- Arc flash visor helmet, Hearing protection, Electrical insulation gloves (class 0), Safety footwear, Class 1 Arc/Flame resistant clothing
HV
Testing for dead
- Arc flash visor helmet (>0.8m), Hearing protection, Electrical insulating gloves, Underglove, Safety footwear, Class 2 Arc/Flame resistant clothing (>0.8m), HV Arc flash kit (<0.8m)

Question 6

The ability to explain or demonstrate what LV isolated tooling is to be used when working near live electrical systems.

Answer 6

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