Tender Summary: Medium Voltage Infrastructure Maintenance (6.6kV & 11kV)

Objectives

The primary objective is to ensure the safe, reliable, and fully compliant operation of medium voltage electrical infrastructure operating at 6.6 kV and 11 kV. This will be achieved through structured preventive maintenance, rigorous electrical testing, and prompt corrective interventions to minimise downtime, extend asset lifespan, and mitigate operational and safety risks.

Scope of Work

The contract covers the maintenance of five electrical substations and associated transformers. Services encompass:

• Substation & Switchgear: Visual and mechanical inspections, cleaning, functional operation and interlock testing, contact resistance measurements, circuit breaker timing tests, lubrication of moving parts, verification of protection and tripping circuits, SF₆ gas checks, and defect identification/reporting.
• Transformers: External condition assessments, oil level and leak checks, transformer oil sampling and analysis, insulation and winding resistance testing, cooling system inspections, Buchholz relay and protection device checks, and earthing verification.
• Cables & Connections: Thermal imaging under load, torque checking of bolted connections, cable termination and joint inspections, sheath integrity testing, cable fault location and repair, and verification of earthing, bonding, and cable routing markers.

Technical Requirements

Bidders must demonstrate proven capability in performing insulation resistance testing, contact resistance measurements, circuit breaker timing tests, protection relay testing, thermographic inspections, and high-voltage (HV) testing. Valid calibration certificates for all designated test equipment are mandatory. A comprehensive safety file must be submitted prior to commencement of work. All services will be governed by the General Conditions of Contract (July 2010). Evaluations follow an 80/20 weighted scoring model, allocating 80% to price competitiveness and 20% to preferential procurement goals.

Skills and Qualification Requirements

Personnel deployed must hold at minimum a diploma in electrical engineering, accompanied by documented authorisations and proven experience in medium voltage infrastructure maintenance. Bidders must provide two reference letters confirming prior successful experience with 6.6 kV and 11 kV systems. A company profile detailing firm background, years of industry experience, and relevant technical capabilities is compulsory. Suppliers must also submit valid Broad-Based Black Economic Empowerment (BBBEE) certificates to claim preference points for historically disadvantaged groups, including entities with at least 51% black ownership, 30% women ownership, or verified disability ownership. Full compliance with standard supply chain disclosure forms and conflict-of-interest declarations is required.

Key Terms and Definitions

• DGA (Dissolved Gas Analysis): Laboratory testing of transformer oil to detect internal faults by identifying hydrogen, methane, ethane, ethylene, and acetylene gases produced by overheating or electrical arcing.
• BDV (Breakdown Voltage): Measurement of the electrical stress an insulating oil can withstand before failing, directly indicating its dielectric strength and contamination levels.
• Buchholz Relay: A protective device installed on oil-filled transformers that automatically detects gas accumulation or abnormal oil flow caused by internal faults, triggering alarms or tripping.
• SF₆ Gas: Sulphur hexafluoride, a highly effective insulating and arc-quenching gas used in high-voltage switchgear; requires specialised monitoring, leak detection, and environmentally compliant handling procedures.
• 80/20 Preference Point System: A public procurement evaluation framework where 80% of the total score is derived from competitive pricing and 20% from socio-economic development goals aligned with national transformation policies.