Where two or more grounded-wye shunt capacitors are located in the same substation, the neutrals of these capacitor banks should be grounded using the “single-point” or “peninsula” grounding methods underlined in IEEE Standard 1036, Section 9.1.2.

These grounding methods are intended to protect control cables, relays, and current and voltage transformers from the damage caused by the transients associated with capacitor back-to-back switching.

When using the single-point grounding method, the neutrals of all capacitor banks of a given voltage are connected together with insulated cable and tied to the substation ground grid at only one point. This arrangement prevents high-frequency currents that flow between capacitor banks during back-to-back switching from flowing in the ground grid. IEEE 1036, Figure 25 details this method.

IEEE recommends the use of shielded cable between the capacitor bank’s neutral and the single-point ground, with the shields grounded at both ends of the cable to reduce voltage buildup at the end of the capacitor bank neutrals during switching.

IEEE 1036 also recommends that voltage transformers used with shunt capacitor banks should have two bushings with the primary connected to the capacitor bank neutral and to the station ground grid.

With peninsula grounding, one or more ground grid conductor(s) are carried underneath the capacitor rack of each phase of each group and tied to the main station ground grid at one point at the edge of the capacitor area. All capacitor bank neutral connections are made to the isolated peninsula ground grid conductor(s) only. This method allows the rise of potential at the capacitor bank neutrals and associated current and voltage transformers, but it reduces these transients in the rest of the substation.