Neutral Point
The common connection point of a star (wye) winding where the three-phase voltage vector sum equals zero.
The neutral point is where three phases of star-connected winding join. Under balanced conditions, vector sum of voltages = zero.
Can be: solidly grounded (most common), resistance grounded (limits fault current), reactance grounded (Peterson coil), isolated. Nameplate specifies: which winding has neutral, BIL level, rated short-time current.
Delta windings lack neutral. For grounding in delta systems, use grounding transformer (zig-zag).
QDTB provides neutral points per project requirements. See grounding guide for selection.
Related Terms
Grounding Transformer
A transformer providing a neutral point for grounding in ungrounded or delta-connected systems.
Zero Sequence Current
Current components equal in all three phases flowing through neutral/ground during unbalanced or fault conditions.
Vector Group
Standardized designation of transformer winding connections and phase displacement between HV and LV.
Wye-Delta Connection
A three-phase connection with one star and one delta winding providing phase shift and harmonic isolation.
More Terms Starting with “N”
No-Load Loss
Power consumed when energized but not supplying load, consisting of core losses (hysteresis + eddy currents).
NEMA Rating
Enclosure protection ratings for electrical equipment specifying protection against environmental hazards.
Nameplate Rating
Manufacturer's certified specifications on the transformer nameplate defining all critical parameters.
Network Protector
An automatic switching device on secondary network systems preventing reverse power flow from distributed generation sources.
More in “Design & Engineering”
Altitude Derating
The reduction in transformer capacity and insulation performance required at high altitudes where air density is lower.
Cooling Class (ONAN/ONAF/ODAF)
Standardized codes describing transformer cooling methods: O=Oil, N=Natural, A=Air, F=Forced, D=Directed flow.
Faraday Shield
An electrostatic shield between transformer windings blocking capacitive coupling of high-frequency noise.
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