What does it mean when people say the grid has “no capacity” for another project?

What We Know

Grid capacity is not one universal number. A node may be constrained by one or more of the following:

• Thermal capacity: a line, cable or transformer could exceed its safe rating.
• Contingency capacity: the system could operate normally but become overloaded if another circuit or transformer fails.
• Minimum local demand: solar output may exceed the electricity being consumed locally, producing excessive reverse power flow.
• Voltage: additional generation could push local voltage above permitted limits.
• Fault level: the connection could raise short-circuit current beyond equipment ratings.
• Protection: existing schemes may no longer detect and isolate faults correctly.
• Power quality: inverter-based generation may create unacceptable harmonics, flicker or rapid voltage changes.
• System strength or stability: the wider system may not be sufficiently robust for additional inverter-based generation without compensating equipment or control capability.
• Physical space: the substation may have no spare bay, busbar position, protection-panel space or suitable land for expansion.
• Committed capacity: the technical headroom may already have been allocated to projects that are not yet operating.
• Operational limits: the project may be connectable only if its exports are curtailed at certain times.

Malaysia’s distribution-connected LSS rules illustrate why solar hosting capacity can be lower than the equipment’s nameplate rating. The guideline considers feeder security, daytime trough demand, transformer loading, voltage rise and fault levels. It specifies, among other criteria, a 2 MW limit for an 11 kV feeder and a transformer penetration limit based on 85% of the daytime trough, subject to the detailed study. Energy Commission: LSS Connection Guideline

“No capacity” should therefore be treated as the beginning of an investigation. The developer needs to establish:

• Which network element or technical criterion is binding?
• Does the constraint occur continuously, seasonally or only during particular contingencies?
• Is the quoted capacity already occupied or merely reserved?
• Could a smaller, controlled or non-firm export connect?
• Would another connection point be less constrained?
• What reinforcement would remove the constraint, and who would pay for it?

People & Organisations

• TNB Grid
• TNB Distribution Network
• Grid System Operator
• Energy Commission
• Single Buyer
• Sabah Electricity
• Sarawak Energy
• Renewable-energy developers
• Power-system consultants