What Is MV Insulated Safety Equipment? Types and Selection Criteria
MV insulated safety equipment is the gloves, hot sticks, insulating stools, voltage detectors and signs that protect staff during switching, voltage checks and rescue in MV substations.
MV insulated safety equipment is the gloves, hot sticks, insulating stools, voltage detectors, rescue hooks and similar gear that insulate staff from live parts or keep them at a distance during switching, voltage checks and emergency rescue in medium-voltage (MV) substations, in front of switchgear cells and in electrical rooms, together with danger warning signs. This equipment does not allow unauthorized persons to work in an MV installation; it is used by trained and authorized staff together with operating instructions and the switching procedure.
Types
| Equipment | What it does | Check before use |
|---|---|---|
| Insulating gloves | Insulate the hand during switching and checking | Visual inspection, inflating to check for holes, test date |
| Hot stick (insulated operating rod) | Allows disconnector and fuse switching from a distance | Cracks, dirt and moisture on the surface; soundness of joints |
| Insulating stool | Insulates the person from the floor during switching | Soundness of the insulating surface and the legs |
| MV voltage detector | Shows whether voltage is present | Trial with the test button or on a known live point |
| Rescue hook | Pulls a person caught by voltage away without contact | Soundness of the insulating handle, hung within easy reach |
| Danger of death sign | Warns of the hazard at the entrance to a live compartment | Legible, visible on the door and in front of the cell |
Selection criteria
- Installation operating voltage: The voltage rating of each item must cover the highest operating voltage of the installation. In Turkey's common 34.5 kV MV distribution networks, equipment rated 36 kV is used.
- Glove class: IEC 60903 divides insulating gloves into classes; 36 kV AC is the use voltage of class 4, the highest class.
- Voltage detector range: The detector's nominal voltage range must cover the installation voltage. A detector made for LV is not used in an MV installation.
- Hot stick and stool ratings: Confirm the insulation voltage of the hot stick and stool and the length of the hot stick in the product datasheet; the hot stick head must suit the disconnector or fuse it will operate.
- Inspection and storage: Store gloves unfolded, away from sunlight and heat; keep the hot stick dry and clean, because dirt and moisture on the surface create a leakage path.
Safe working sequence
For de-energized work the sequence is: disconnect, lock out and tag against reclosing, verify the absence of voltage with the voltage detector, earth and short-circuit, and cover or keep away from nearby live parts. Insulated equipment does not replace this sequence.
Common mistakes
- Switching MV with LV gloves: If the glove class does not match the installation voltage, it provides no insulation.
- Using a voltage detector without testing it: A "no voltage" indication from an untested detector cannot be trusted.
- Using gloves without an inflation check or when wet: Small holes that cannot be seen spoil the insulation.
MV insulated safety equipment in the catalog
The MV Insulated Safety Equipment, Gloves and Warning Signs category has 6 active products from MAS: 36 kV insulating gloves (MAS-ELDV36kV), hot stick (MAS-STNK), insulating stool (MAS-IZLSHP), MV voltage detector (MAS-OGKNTKL), rescue hook (MAS-OGHYTKRT) and danger of death sign (MAS-DKTLVH). Prices for these products are given on request. For voltage checks in LV installations, see the voltage and continuity testers category.
Frequently asked questions
Where are 36 kV gloves used?
In MV installations whose highest operating voltage does not exceed 36 kV, for example substations on 34.5 kV distribution networks.
How is an MV voltage detector used?
First confirm that the detector works with its test button or on a known live point. Then check each phase separately and test the detector again.
How often are insulating gloves checked?
They are inspected visually and inflated to check for holes before every use. The interval of periodic electrical testing is set by the manufacturer's instructions and the operating procedure; gloves past their test date are not used.
What is the difference between an insulating stool and an insulating mat?
An insulating stool is portable and placed at the point where switching is done. An insulating mat is laid on the floor in front of the cells and stays in place permanently.