Transmission sector stakeholders have decided to adopt new measures to lower the high failure rate of electricity distribution transformers, achieve uniformity in specifications across utilities and manufacturers, and reduce replacement delays.

At a recent meeting of the standardization cell convened by the Central Electricity Authority (CEA), stakeholders flagged moisture ingress, poor sealing, and non-uniform components as major reasons for transformer breakdowns.

It was announced in the meeting that the national distribution transformer failure rate averages around 10% or nearly 1.3 million failures annually. Kerala had a failure rate of 1.9%, while some northern states exceeded 20%.

In contrast, private utilities, including Tata Power-DDL and CESL (Kolkata), have a low failure rate of about 0.5%.

In October, a CEA report said a large number of transformer failure incidents go unreported. It noted that many transformers installed in Indian utilities have failed within the first few years of service, which is a matter of concern.

Besides transformers, transmission towers have also experienced failures. In 2024, there were 76 extra-high-voltage transmission line tower failures across 28 transmission lines, including 220 kV, 400 kV, and 765 kV AC lines, as reported by 12 public and private power utilities

Best Practices

The standardization cell meeting identified moisture ingress (accounting for 90% of the failures) as the most recurring factor behind transformer failures, often linked to inadequate sealing, poor breather performance, and weak joint integrity.

It decided to adopt modern sealing mechanisms, such as O-ring gaskets; change the transformer design to provide a neutral connection at the base for uniformity; and use tin-plated connections for joints in the winding or conductor to lower contact resistance and improve connectivity.

The meeting called for wider standardization of critical parts and materials across manufacturers to improve interchangeability and maintenance efficiency. It recommended third-party power-quality audits, voltage tracking, and the use of temperature sensors in oil and windings to detect stress or fault conditions early.

The meeting also proposed drafting a revised specification aligned with IS 1180 for transformers used in underground cable networks and establishing a periodic review mechanism to track adoption and performance outcomes.

The CEA will conduct training workshops for distribution companies’ engineers and transformer manufacturers on failure prevention, testing protocols, and maintenance best practices.

Tata Power-DDL told the meeting that its patented breather design and strict inspection protocols have helped keep failure rates below 1%, with a continuing push toward the 0.5% target.

CESC Kolkata said remote monitoring, health indexing, improved insulation, redesigned radiator/header systems, and third-party inspections had helped it to keep transformer failure rates around 0.4–0.5%.