Knowledge Center

Safety First: Safe & Secure Bushing Monitoring

2nd June 2023
Tap adapter

Let’s talk Tap Adapters!

With between 15 - 30% of all transformer failures being attributed to bushings, it is important that they are continuously monitored. To monitor bushings there are 2 key methods: thermal and electrical.

Electrical method

It is now widely accepted in the industry that the electrical method is the best and most reliable option. This process requires connecting to the test tap of the bushing using a tap adapter.

Now...onto the Tap Adapter

At Camlin Energy we understand the key concerns facing asset managers, with safety being a critical concern. We took the decision to manufacture our tap adapters in-house giving us full control over the design and manufacturing process.

Our tap adapter development was focused on resolving the key issues:

  • Operator safety
  • Bushing reliability

Did you know? Since 2015 we have installed more than 2000 tap adapter for bushing monitoring!

We have listened to our customers and partners regarding concerns in connection to the bushings of their transformers. With safety being a number 1 priority, we have engineered our tap adapter to address customer concerns over operator, safety, whilst ensuring efficient monitoring of this vital asset.

Electrical design considerations

It is critical to guarantee that the test tap is safely grounded to ensure it does not become floating. We therefore implemented electronics, protections and contacts to guarantee the safe grounding.

To enhance the electronic circuitry, we included:

  • 2 x Resistors – ensuring safe output voltage during connection interruptions
  • 2 x Metal Oxide Varistors - protecting electronic circuitry against transient voltages
  • 2 x 90V Gas Discharge Tubes - limits output signals during surges
What if the measuring impedance fails?

The redundancy protection combined with the over-rating criteria for the components makes this scenario almost impossible. In the unlikely event that one or both of the measuring impedances were to fail, the TOTUS monitoring system would activate an alarm.

What if there is a break in the cable connection?

The electronics inside the tap adapter protects against any direct contact should the signal cable be accidentally damaged or severed; the designed guarantees the voltage is maintained <1Vrms. Additionally, if a disconnection were to occur, the operator would be notified by a malfunction alarm from TOTUS.

Mechanical design considerations

The initial mechanical design concept plan was to split assembly into two components; the head and the body in order to:

  • Prioritize attention on the bushing tap thread during installation
  • Enable a simple process for the Offline Test Tool application
  • Facilitate existing component refurbishment when bushing replacements are required

Tap Adapter Head

The tap adapter head acts as a mechanical connection point between the bushings and the electronic circuitry. To ensure the successful design and installation of components, every site undergoes a detailed evaluation to determine the specific mechanical requirements, defining the applicable design. The sealing of the adapter head is designed to replicate the original bushing cap.

Tap Adapter Body

A key element of the design is focused on all the sealing components of the adapter body, in particular, ensuring the sealing elements are protected from UV exposure and water ingress.

The Harting connector is the signal cable, plug and play connection point designed to eliminate two key issues:

  • Water ingress – a strong cable gland and additional heat shrink cover secure the connection from moisture
  • Mechanical strength – the metal structure of the connector provides optimal strength against torque and rotational movement

An additional feature is a transparent viewing window on the tap adapter body. This enables verification of the installation by confirming the internal shaft is in contact with the bushing test tap hot pin.

The Camlin Energy test tap adapter is rated as IP67

Offline Test Tool

Offline testing is an important procedure, even for those who have adopted online monitoring. Access to perform offline testing, therefore, is a key requirement of the design. Our offline test tool has been developed in order to work safely in conjunction with the tap adapter, enabling routine offline bushing tests to be conducted safely without removing the overall device, without operating the bushing test tap thread.