Surge arresters are essential components in modern electrical systems, protecting critical infrastructure from overvoltages caused by lightning strikes and switching operations. However, these devices do not last forever. As they age, their performance deteriorates, and instead of providing protection, they may become a source of electrical faults.

This article discusses the risks associated with an out-of-date surge arrester, the types of faults it can trigger, and other problems that may result from its continued use.

What Is an Out-of-Date Surge Arrester?

An out-of-date surge arrester refers to a device that has exceeded its expected service life, has been exposed to damaging environmental conditions, or no longer meets the performance requirements of the system. Over time, factors such as pollution, moisture, heat, and frequent surges contribute to the degradation of its internal and external components.

Modern metal oxide varistor (MOV) surge arresters typically have a lifespan of 10 to 20 years. However, poor maintenance, high stress environments, and frequent surge events can shorten this period significantly.

How an Out-of-Date Surge Arrester Causes Faults

1. Decreased Insulation Integrity

Aging arresters may develop cracks or moisture ingress that reduces their insulation resistance. This can result in:

  • Leakage current that stresses insulation further
  • Internal discharges that damage internal components
  • Increased risk of surface tracking or flashover

2. Thermal Instability and Runaway

Degraded materials in an arrester can lead to internal heating. Over time, this can result in thermal runaway, where the temperature increases uncontrollably, potentially causing:

  • Internal breakdown
  • Smoke or fire
  • Violent rupture or explosion of the arrester housing

3. Persistent Fault Current

A faulty arrester might fail to extinguish the follow current after a surge has passed. This condition can cause:

  • Sustained faults within the network
  • Tripping of circuit breakers or protection systems
  • Damage to nearby equipment such as transformers or switchgear

Other Consequences of Using an Out-of-Date Surge Arrester

Equipment Downtime

Unexpected arrester failure can interrupt operations and lead to prolonged downtime for diagnostics and repairs.

Increased Maintenance and Inspection Effort

Outdated arresters may require more frequent manual inspections and testing, diverting resources from other operational needs.

Safety Risks

In extreme cases, a failing arrester can explode under pressure, scattering debris and posing a danger to personnel working nearby.

Reduced System Reliability

A network that relies on aging or mismatched arresters may experience uneven protection, increasing the likelihood of cascading equipment failures during overvoltage events.

Signs That a Surge Arrester Is No Longer Reliable

Identifying when an arrester is out of date can prevent failures. Warning signs include:

  • Visible surface damage, such as cracks or chalking
  • Discoloration or evidence of moisture intrusion
  • Abnormal leakage current levels
  • Frequent protection device activations during normal operations

Prevention and Best Practices

To mitigate risks, asset managers and maintenance teams should:

  • Conduct periodic visual and infrared inspections
  • Monitor leakage current levels and trends over time
  • Maintain detailed records of installation and service life
  • Replace arresters proactively based on age, condition, and system upgrades

An out-of-date surge arrester not only loses its effectiveness but can also introduce new risks to the very systems it is meant to protect. From internal breakdowns and equipment damage to safety concerns and system downtime, the consequences of ignoring arrester aging can be severe.

Regular monitoring and timely replacement are crucial to maintaining the reliability and safety of any electrical network.