About the Safe Working Clearance
Safe working clearance (SWC) defines the minimum distance between a person and a live electrical conductor or equipment to prevent electric shock or arc flash injury — essential for anyone working on or near energised solar, BESS, or substation equipment.
How to calculate it
- 1SWC depends on voltage level: at LT (< 1,000 V AC) — minimum 300 mm; at 11 kV — 900 mm; at 33 kV — 1,200 mm; at 132 kV — 2,000 mm (per IE Rules and IS 5216).
- 2These are approach boundaries, not working distances — work on energised HT equipment requires live-line tools and specialist training.
- 3For solar DC systems: although classed as LT (< 1,500 V DC), the DC shock hazard is higher than equivalent AC — maintain 500 mm minimum clearance from uninsulated DC conductors.
- 4Permit to Work (PTW) system: before any work near energised equipment, issue a formal PTW that specifies the safe isolation boundary, the SWC, and the permits required.
- 5Arc flash boundary: for HT equipment, calculate the arc flash incident energy (per IEEE 1584) and specify the arc flash protection boundary and PPE level.
Worked example
A maintenance technician accessing an AJB on a 500 kWp plant: DC system voltage 600–900 V. The AJB string fuses are at 900 V DC. SWC = 500 mm minimum from uninsulated busbars. Before opening the AJB: isolate the strings (open string fuse holders), verify voltage with a meter, then work. If working with the AJB energised (e.g., taking voltage readings): insulated gloves rated for 1,000 V DC and face shield required.
What you can calculate
- IE Rules 1956 Reg 64
- LT to HV
- Pass/Fail
- Safety margin
Standards & references
Frequently asked questions
Can solar panels be made safe for working on the roof?
Solar panels cannot be completely de-energised during daylight hours — they continue to generate DC voltage as long as light falls on them. To work safely: (1) block sunlight with opaque covers or work at night/overcast conditions; (2) isolate at the inverter DC isolator and AJB to remove current path; (3) use insulated tools and 1,000 V rated gloves. Never assume a panel is safe to touch without verifying with a calibrated DC meter.
What PPE is required for solar electrical work in India?
For LT work (< 1,000 V): insulated gloves (class 0 or 1, 500 V rated), safety glasses, and insulated hand tools (IEC 60900). For DC systems up to 1,500 V: class 1 or 2 gloves (rated 7,500 V), face shield, and fire-retardant clothing. For HT work (> 1,000 V): only licensed electrical workers with live-line training, rated HV gloves, hot sticks, and arc flash PPE may work on energised equipment. IS 5216 specifies these requirements.
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