Accessories and ancillaries

Oil Temperature Indicators are used to monitor the temperature of the insulating oil within the transformer's tank. It is crucial for observing overheating of the transformer's insulating oil. High oil temperatures can result from factors such as load variations, ambient temperature changes, and internal faults. Monitoring oil temperature helps manage the transformer's cooling system. Cooling mechanisms, such as fans, can be activated if the oil temperature exceeds safe limits. By monitoring oil temperature trends over time, maintenance personnel can identify potential issues and schedule maintenance activities proactively. Monitoring oil temperature also contributes to maintaining the quality of the insulating oil. Elevated temperatures can accelerate oil degradation, leading to reduced insulating properties.

This capillary-based, mechanical, remote-indicating thermometer features configurations for oil temperature measurement with up to 6 flexible switches for alarm, trip, and cooling system functions. Maintaining proper oil temperature ensures the optimal performance and reliability of the transformer in various operating conditions.

Winding Temperature Indicators are critical devices used in power and distribution transformers to monitor and indicate the temperature of the transformer windings, which are the major conductive components carrying current. Unlike oil temperature indicators, which monitor the oil surrounding the windings, WTIs measure the actual winding temperature, which tends to run hotter than the oil. This gives a more accurate picture of transformer load stress and its proximity to thermal limits.

Heat is generated during operation due to the flow of electrical current through a transformer's windings. Accurate temperature monitoring contributes to effective asset management by optimising maintenance schedules and extending transformer lifespans. Winding temperature indicators are designed to activate alarms or trips if temperatures exceed safe limits. They could provide input to cooling systems (like fans or pumps) to maintain safe operating temperatures, and some advanced models can record historical temperature data for trending and diagnostics.

The Ashridge 852 WTI & OTI provides an ultra-precise reading by continuously measuring the winding temperature and the oil temperature and displaying the data on a dual display. Top oil temperature measurements and the winding current are combined with Ashridge's algorithm, which is based on the IEC 354 standard, to provide accurate temperature readings. The extensive range includes alarm relay output, data logging, a wide range of CT inputs, dual display and an intelligent cooling control system with ‘deviation from normal’ alarms to ensure optimal asset life and protection for the transformer.

For accurate temperature readings and data logging, the Ashridge software provides a "compare settings with template" facility and downloads the settings for incorporation into documentation or archiving. Understanding the transformer lifespan and regularly examining the temperature increase the safety of the transformer and the personnel working on it. Proper temperature monitoring contributes to effective asset management by optimising maintenance schedules and extending the lifespan of transformers.

A bund, also known as a containment pit or catchment area, is a secondary containment system designed to contain and prevent the spread of oil in case of a leak, spill, or rupture of transformer radiators, main tank or other components. The bund is constructed around the transformer and is designed to hold 110% of the total liquid in the transformer, ensuring that any leaks or spills are prevented from reaching the surrounding environment.

The primary purpose of the bund is to contain oil leaks, preventing environmental contamination or hazards. Bunds are critical for preventing oil spills from reaching the soil and water, reducing the potential harm to ecosystems and groundwater. Compliance with environmental regulations and standards is a key application of bunds. Bund mitigates the financial and legal risks associated with environmental pollution resulting from oil leaks or spills.

Bund filters are designed to capture hydrocarbon pollutants while letting clean rainwater pass through and safely discharge into the environment. By stopping bunds from filling up and spilling over, they reduce the need for costly oil-water separators or vacuum tanker services.

Anti-Vibration Pads are positioned beneath the transformer to reduce or eliminate the transmission of vibrations from the transformer to the surrounding structure. These pads are made from materials like rubber, neoprene, or composite materials that can absorb and dampen vibrations, protecting both the transformer and the surrounding infrastructure whilst reducing noise. Minimising vibrations can increase the lifespan of transformers and other equipment as a result of the reduced wear and tear caused by mechanical stresses.

Anti-Vibration Pads are soft, elastic materials that act as a buffer between the transformer and its foundation or supporting structure. Power transformers and medium to large distribution transformers can generate significant vibrations due to electrical activity, mechanical movement, and cooling processes (such as the operation of fans or pumps). They can benefit from Anti-Vibration Pads as noise and vibrations are dampened that might otherwise be felt by nearby residents or occupants. In environments where sensitive equipment or precision instruments are located near transformers, such as in hospitals or research facilities, anti-vibration pads help prevent vibrations from interfering with the operation of these devices. Transformers located near highways or railway tracks can be subjected to vibrations from passing vehicles or trains. Anti-vibration pads help mitigate the impact of these external vibrations. Vibrations can generate audible noise, especially when they’re transmitted to the building structure. Anti-vibration pads reduce this noise, contributing to a quieter environment.

The conservator helps manage the expansion and contraction of insulating oil due to temperature changes. This is important for ensuring proper cooling and insulation properties of the transformer. Conservators prevent overpressure from building up inside the transformer, which could result in mechanical stress or damage to components.

As gases are generated within the transformer due to normal operation or faults, the conservator allows these gases to escape safely, preventing pressure build-up. The conservator reduces oil surface contact from surrounding air, thus minimising the ingress of moisture or contaminants. By providing space for oil expansion and contraction, the conservator minimises exposure to air, reducing the risk of oil oxidation.

Oil- and gas-actuated protection relays are used on liquid-insulated transformers to provide protection from electrical faults occurring inside the transformer, accompanied by gas generation or oil surge onto the conservator. The Buchholz relay is primarily designed to detect the presence of gases generated due to electrical faults, such as short circuits or insulation breakdown, occurring within the transformer.

The primary application of a Buchholz relay is to detect internal faults within the transformer, such as short circuits between windings, inter-turn faults, or arcing. Rapid gas generation within the transformer's insulating oil can indicate insulation degradation, overheating, or other issues, providing early warning of potential problems. The presence of gas can indicate the occurrence of faults within the transformer. Buchholz relays help detect these conditions. Early detection of internal faults by the relay helps prevent major failures that could lead to costly downtime and extensive repairs. By analysing the composition of the gases collected by the Buchholz relay, maintenance personnel can gain insights into the nature of the fault and the transformer's condition.

The Buchholz relay's Gas Collecting Device is a small chamber with three functions: extracting gas from the Buchholz relay and venting it from the system, testing both the alarm and trip circuits of the Buchholz relay, and draining oil from the Buchholz relay.

An Oil Surge Relay is a protective device designed to detect sudden or abnormal changes in the oil level or pressure inside the transformer, especially around the tap changer. The tap changer is a crucial component of the transformer that adjusts the voltage ratio by selecting different taps on the transformer windings.

The oil surge relay is designed to safeguard the on-load tap-changer and transformer in the event of a fault occurring within the tap-changer or selector switch oil compartment. It activates by tripping when the oil flow rate between the tap-changer head and the conservator surpasses a predetermined threshold.

An aircell is a flexible diaphragm or rubber bag within the transformer's conservator that holds air. Its primary function is to provide a space for the transformer’s oil to expand and contract as the temperature changes without letting it come into contact with the outside atmospheric air, which can introduce moisture and oxygen, degrading the oil. The Aircell expands or contracts by absorbing or releasing air, as the oil level changes due to temperature. By allowing for oil expansion and contraction, the Aircell helps maintain a steady internal pressure, preventing tank or conservator damage due to pressure changes.

A rupture relay is a safety device used in transformers to monitor the integrity of the transformer’s oil system, particularly in relation to the Aircell. If the Aircell fails or the oil pressure reaches dangerous levels, it can cause the rupture of the conservator or other components. The rupture relay acts as a safeguard, detecting any sudden and excessive pressure increase within the transformer’s oil system. If the pressure exceeds safe levels, the rupture relay activates, either signalling an alarm or automatically triggering the transformer to shut down to avoid damage or catastrophic failure.

Offering protection against high humidity, pressure variations, dielectric loss, and outgassing, the Brownell Transformer Breather absorbs moisture from the air, maintaining dryness. It features a shatterproof, UV-stabilised polycarbonate cylinder. The Envirogel Orange to Green colour-changing silica gel allows for visual recognition when the unit needs replacing or refilling.

The primary purpose of a transformer breather is to control the moisture levels in the conservator tank and the insulating oil. Moisture can lead to oxidation or degrade the oil's insulating properties and cause insulation breakdown. The breather's air filter prevents dust, dirt, and other contaminants from entering the tank and contaminating the oil. Transformer breathers ensure the tank remains at atmospheric pressure by allowing air movement. This prevents overpressure occurrences that could damage the transformer. Monitoring the colour indicator of the breather allows service personnel to schedule maintenance and desiccant replacement when needed.

Pressure and/or vacuum indicator for accurate representation of the pressure state inside the transformer, featuring a 3.5-inch (88.9 mm) dial with at least 180° of angular pointer deflection for easy reading at a glance and available in a wide variety of pressure ranges and scales for many applications.

PVGs play a vital role in assessing a transformer's overall health. Abnormal pressure or vacuum readings could indicate internal issues such as partial discharges, winding faults, or oil degradation. Monitoring pressure and vacuum levels helps prevent catastrophic failures. Overpressure situations could lead to oil leaks, insulation breakdown, or even explosions, while excessive vacuum could cause moisture and contaminants to enter the transformer.

By analysing pressure and vacuum trends over time, maintenance professionals can predict when a transformer might require maintenance. This approach can help avoid unplanned downtime and reduce operational costs. Pressure and vacuum monitoring contribute to the safety of the transformer and the personnel working around it. Early detection of abnormal conditions allows for timely actions. Maintaining proper pressure and vacuum levels ensures the transformer operates within its designed parameters, optimising its efficiency and lifespan.

Mechanical overpressure protection device provides pressure-relief on transformers during overpressure conditions, automatically resealing once pressure has subsided. PRDs are designed to release excess pressure in a controlled manner to avoid transformer tank rupture or other potential hazards.

The primary purpose of a PRD is to prevent the buildup of excessive pressure within the transformer tank. Excessive pressure can be caused by events such as internal electrical faults, short circuits, and rapid heating. By releasing pressure in a controlled manner, PRDs prevent the transformer tank from rupturing due to overpressure, which could result in oil spills, fires, or, in severe cases, explosions.

PRD helps avoid the ejection of insulating oil from the transformer tank, which can occur if pressure is not relieved properly. Oil ejection poses safety risks and can cause environmental damage. PRDs can be manually activated during maintenance or emergency situations to release pressure from the transformer.

Magnetic Oil Level Gauge is used to measure the level of insulating oil within the transformer tank. Specifically designed for use on power transformers, this device gives an analogue indication of the oil level inside the conservator by a graduated dial with arrow and one or more electric signals when the oil inside the conservator reaches the maximum or minimum level.

The primary purpose of the MOG is to monitor the oil level within the transformer tank. Adequate oil levels are crucial for proper cooling and insulation. Low oil levels can lead to overheating, reduced insulation effectiveness, and potential damage to the transformer. Consistent monitoring of oil levels over time can help predict potential maintenance needs. Significant changes in oil levels indicate leaks or other issues requiring attention. MOGs assist in maintaining the integrity of the transformer's containment system.

Additional cooling mechanisms are sometimes required in transformers to dissipate excess heat generated during their operation. Transformers generate heat due to core losses, winding resistance, and other factors. Proper cooling methods, such as Forced-Fan Cooling (ONAF), maintain their efficiency and prevent damage from overheating.

Power Transformers used in electrical substations and distribution networks can generate significant heat due to the high voltages and currents they handle. Forced-fan cooling is commonly used in these transformers to ensure efficient operation and prevent overheating. Transformers used in industrial settings, such as manufacturing plants and large facilities, often require forced fan cooling to handle the heat generated by heavy loads and continuous operation. Transformers that experience varying load conditions or operate under heavy loads periodically may use forced fan cooling to maintain stable temperatures during peak demand. Transformers located in areas with high ambient temperatures or limited ventilation can greatly benefit from forced-fan cooling to ensure consistent performance.

An oil flow indicator is a device used to monitor and display the movement of oil within the transformer. It helps operators ensure that oil flows properly through the cooling system, which is crucial for maintaining transformer performance and preventing overheating. The indicator provides a visual or mechanical signal if there is a problem, such as low oil flow, which a pump failure or oil blockage could cause. Oil Flow Indicators provide a clear, real-time indication of whether oil flows correctly through the system. Detecting abnormal oil flow conditions helps prevent overheating and protects the transformer’s insulation from damage.

The Oil Pumps in a transformer are responsible for circulating the oil through the transformer’s core and coils to transfer heat away from the transformer’s active parts. This helps maintain the temperature of the transformer within safe operational limits, preventing overheating that could damage the insulation or other internal components. They ensure that the oil flows through the transformer, maintaining consistent cooling of the internal components. Therefore, they help stabilise the transformer’s temperature by dissipating heat generated by the electrical load. Proper cooling via oil circulation prolongs the life of the transformer’s insulation and other components. In some designs, pumps are also used to maintain adequate pressure levels in the oil system.

An OLTC maximises energy savings by maintaining a consistent secondary voltage despite variations in input voltage and load conditions. Achieved by adjusting the turns ratio of a transformer’s windings whilst the transformer is energised and in operation, OLTC can perform up to 500,000 maintenance-free operations, outliving the transformer.

OLTCs are primarily used to regulate the output voltage of a transformer to maintain a steady voltage level at the load terminals. This is important for delivering consistent and reliable power to consumers. As the electrical load on the transformer fluctuates, the OLTC ensures that the output voltage remains within the pre-defined voltage range. This is particularly important in distribution networks with varying load demands or fluctuating voltage supply, causing over- or under-voltage issues. OLTCs can reduce the voltage to prevent transformer overloading during periods of high load. This can help prevent overheating and extend the transformer’s operational life.

The Automatic Voltage Regulation (AVR) Relay is used in conjunction with on-load tap changers (OLTC) on Power Transformers to monitor and automatically regulate the transformer's output voltage. It plays a crucial role in maintaining the voltage within a pre-defined range and preventing voltage-related issues that could affect the performance of the transformer and connected equipment.

AVR Relays are critical for maintaining a stable power supply and preventing voltage fluctuations that could damage equipment or disrupt operations. AVR relays help ensure the voltage remains within acceptable limits despite load or unstable supply and fluctuations. They can quickly respond to sudden voltage surges or dips caused by faults or disturbances in the power grid and adjust the tap settings to bring the voltage back to specified levels. In remote substations or substations that are part of a larger network, AVR relays provide a means of automatic response, enhancing the efficiency of voltage regulation.

Marshalling boxes serve as a central point for organising and connecting various electrical cables and wires associated with different components of the system. They play a crucial role in maintaining a clean and organised wiring arrangement, facilitating maintenance, and ensuring an organised arrangement to avoid errors.

Designed by our engineers and assembled in our "bungalow" in Leeds, marshalling boxes organise the wiring and connections between the transformer and the necessary monitoring and protection systems, including connections to temperature sensors, pressure sensors, and protection devices. In systems where multiple cables from different sources need to be interconnected, such as in complex transformer installations, marshalling boxes simplify the wiring arrangement, making it more manageable and efficient.