•Either winding can be left ungrounded, or grounded at any point without affecting the grounding or the voltage of the other winding. System 3 has an ungrounded single-phase transformer secondary, and System 4 has a grounded wye transformer secondary. In contrast, any grounding problem in grounding systems 2, 3, or 4 will not effect its respective primary grounding system due to its primary delta windings. Ungrounded interconnection can be provided for inverter-based systems requiring it. This capacitance becomes part of our circuit that already includes cable inductance and resistance. This is a very unusual setup to the best of my knowledge in that ungrounded systems are normally fed from delta-transformer windings. Secondary and low side (and LV) terms are used interchangeably; ... that a HV Wye-grounded transformer connection has different voltage and current characteristics compared to the HV Wye-ungrounded or a HV Delta connection during an open phase condition. Voltage protection on ungrounded systems requires a connection to three phase instrument voltage s transformer (VTs). primary is hooked in delta, secondary in wye and grounded. System 2 has an ungrounded delta transformer secondary, and an ungrounded single-phase transformer primary. Disadvantages of Delta-Delta or Ungrounded Wye-Delta Connection: i. Utility-side SLG faults are difficult to detect. This system is shown in Fig. The secondary windings of the transformer are connected in delta configuration and the system feeds an ungrounded load. If one conductor or the other is grounded, the system’s phase-to-ground voltage is 120V. The NEC still requires that the grounding electrode conductor be sized to the secondary ungrounded conductors. Abstract: This paper documents the detailed analysis of the three-phase ungrounded wye-delta transformer bank serving a combination three-phase induction motor and single-phase lighting load. The distribution feeders are three-wire three-phase and two-wire single-phase circuits. The wye-delta grounding transformer allows the flow of the exciting current triple-harmonics, thereby achieving a sinusoidal flux wave and inhibiting the triple-harmonics of the line-to-neutral voltage. Secondary can either be center grounded, corner grounded or ungrounded. Figure 5 shows a wye-delta grounding transformer with the primary grounded, connected to the secondary winding of the ungrounded wye-wye bank. For ungrounded systems, the greatest voltage between the given conductor and any other circuit conductor is also the phase-to-ground voltage. It is always recommended that Wye Delta transformers be connected such that the Wye Primary is not grounded. detecting and protecting against ground faults for an ungrounded system. See Figure 1. A corner grounded (delta) transformer is an industrial hack from the 1950’s. Ferroresonance may be eliminated by using a single primary wye with dual secondary VTs where one VT secondary set is wye connected and the other VT secondary set is a broken delta : Can only detect line faults. Zero- Specifically this includes ungrounded Delta, ungrounded wye and impedance grounded wye systems. Ungrounded systems have the secondary windings of the distribution substation transformer connected either in ungrounded delta or ungrounded wye, with the former connection being more common. Figure 1 below. However, with an ungrounded Wye Delta connection it is possible to back feed significant voltage when one primary phase is opened. This is a very important distinction to make and keep in mind as we go through the analysis. This method of metering is applied to