Objectives

The primary objective of this tender is to develop and implement a Self-Resetting Pole Mounted Transformer solution that can detect overload conditions, disconnect the load when thermal limits are reached, and automatically reconnect once the transformer has cooled to acceptable levels. This aims to extend transformer lifespan, reduce vandalism and theft risks, and minimize onsite operator intervention and customer outages.

Scope

Proposals are sought for a self-resetting transformer system that:

• Detects overload conditions of pole-mounted transformers.
• Disconnects the LV load (400V) when thermal limits are exceeded.
• Automatically reconnects the load after the transformer cools down.
• Fits within an enclosure attached to the transformer tank, with dimensions approximately 575mm x 650mm x 279mm.
• Utilizes techniques similar to LV motor thermal protection, among other possible solutions.

Technical Requirements

• The system must monitor transformer oil temperature and trip/load disconnect at a thermal set point.
• Automatic reconnection should occur once the temperature recovers to a safe level.
• The solution should be capable of fitting inside an enclosure attached to the transformer tank.
• The enclosure dimensions are specified as length 575mm, height 650mm, depth 279mm.
• The system should be compatible with existing MV pole-mounted transformers and incorporate proven thermal protection techniques.

Skills Requirements

• Design and engineering expertise in transformer thermal protection systems.
• Experience in developing self-resetting overload protection solutions for pole-mounted transformers.
• Capability to design compact, enclosure-compatible electronic systems.
• Knowledge of oil temperature monitoring, load disconnection, and automatic reconnection technologies.
• Proficiency in integrating solutions with existing Eskom infrastructure and standards.
• Ability to provide technical documentation, testing, and validation of the proposed system.