Voltage Fluctuation From the Grid: How to Protect Your Equipment With Surge Protection and Stabilisers

Ask any facility manager in Nigeria and they will describe the same problems: lights that dim and brighten, air conditioners that fail early, electronics that die after a storm, and the bang when grid supply returns after an outage. Unstable voltage costs businesses and homes a great deal in damaged equipment. Most of that damage can be prevented.

The main voltage problems

• Surges and spikes: very short, high-voltage pulses from lightning, switching on the network, or supply being restored.
• Overvoltage: supply voltage staying well above normal for long periods.
• Undervoltage and sags: low voltage that makes motors run hot and stall.
• Lost or broken neutral: one of the most damaging faults, it can push single-phase loads far above their rated voltage.
• Phase loss: three-phase motors running on two phases overheat and burn out.

Layer 1: Good earthing

Surge protection only works if it has a low-resistance earth to divert the surge into. Check your earthing first. Read why earth resistance changes between seasons.

Layer 2: Surge protection devices (SPDs)

SPDs divert surge energy to earth before it reaches equipment. They work best in stages:

• At the main switchboard: to handle large surges coming in from the network or lightning.
• At distribution boards: to catch remaining surges closer to the loads.
• At sensitive equipment: for servers, control systems and medical equipment.

SPDs wear out after absorbing surges. Check their status indicators regularly and replace them when they show end of life.

Layer 3: Voltage regulation

Where supply voltage swings high or low for long periods, an automatic voltage regulator or stabiliser keeps the output within limits. Size it for the real load, including motor starting current, and buy from reputable suppliers.

Layer 4: Monitoring and protection relays

• Phase failure and phase sequence relays disconnect three-phase motors when a phase is lost or reversed.
• Over and undervoltage relays disconnect equipment, or hold off reconnection until supply is stable.
• Time delays on restoration stop equipment restarting during the unstable seconds after grid supply returns.

Layer 5: Lightning protection

Tall buildings, warehouses and telecom structures should have a lightning protection system that safely carries strikes to earth, working together with the SPDs.

Practical checklist

• Test your earthing
• Fit SPDs at the main board and key distribution boards
• Fit phase-failure protection on three-phase motors
• Use stabilisers where voltage is persistently out of range
• Set ATS and changeover time delays so loads reconnect only when supply is stable

For more ways to protect your installation and cut costs, see our tips for reducing electricity bills.

Talk to Corustar

Corustar Technological Services is an electrical engineering contractor based in Ikeja, Lagos, working across Nigeria. See our Earthing & Lightning Protection service, request a quote, or call +234 816 976 9672. For outages and faults, call our 24/7 emergency line on 0705 739 9297.