Surge Arrester Replacement: A System-Duty Checklist for Industrial Transformer Sites

Start with the system, not the old label

Metal-oxide surge arresters protect by limiting overvoltage at the equipment terminal. The replacement must fit the actual network grounding arrangement and abnormal system conditions, as well as the old mounting position. A matching physical housing does not establish correct protection duty.

Information to collect before RFQ

• Network: nominal voltage, highest system voltage, frequency and neutral grounding arrangement.
• Duty: the old arrester Uc and Ur, known temporary-overvoltage conditions, fault-clearing time and any utility specification.
• Protection coordination: transformer insulation level, lead length and required protective level; have the engineer confirm the coordination.
• Installation: polymer or porcelain preference, bracket centres, terminal hardware, earth lead route, clearances and pollution environment.
• Evidence: nameplate photos, surge counter or disconnector requirements, drawings, test records and quantity by phase.

Make the quotation comparable

Ask suppliers to state Uc, Ur, nominal discharge current, line-discharge or energy class where applicable, protective levels, housing material, creepage, accessories and referenced standard. Keep these values beside the existing duty and flag any value that has not been confirmed by the owner or system engineer.

Replacement and close-out controls

De-energisation, isolation, earthing and testing must follow the site’s approved procedure. After installation, inspect terminal contact, short and direct earth connection, clearances, mounting rigidity and nameplate orientation. Record the installed model, serial number and commissioning observations against the asset tag for the next maintenance cycle.

Send the old arrester nameplate, system voltage and a photo of the installed arrangement for a documented replacement review.