Why CT star point is grounded?

Transformer star point is grounded to provide a path to (1) triplen harmonic currents (2) zero sequence currents. These currents are in-phase, and therefore, they need a return path to flow. This is important because in the absence of a path for above currents, voltages will have unbalance and waveform distortion.

What do you understand by the star point of a load?

This just means that all the current going out through a transformer winding will return to the same point via one of the live conductors (either lines or neutral depending on the load configuration).

Why does the earth star point?

The star point is called the neutral. It is common to all 3 phase windings and used as the return wire for all 3 phases. In most systems there is an earth connection where the metal surround of the appliance is grounded so in the event of a fault any leakage or fault current is conducted to ground.

Is a star point a neutral?

Star or Wye (Y) Connection. In star connection, three similar ends (start or finish) of the three windings are joined together at a common point. This point is known as star point or neutral point. The three conductors meeting at star point are replaced by a single conductor known as neutral conductor (or neutral).

Why CT S2 is grounded?

To prevent the secondary circuits from attaining dangerously high potential to ground, these circuits have to be grounded. Connect either the S1 terminal or the S2 terminal to ground. For protective relays, ground the terminal that is nearest to the protected objects.

What is star star connection?

Star-star (Y-Y) Star-star connection is generally used for small, high-voltage transformers. The ratio of line voltages on the primary side and the secondary side is equal to the transformation ratio of the transformers. Line voltages on both sides are in phase with each other.

Why is grounding needed?

Grounding helps protect you and your home from the dangers of damaged circuits or electrical overloads. When power surges happen, the excess electricity introduced to the system could leap out of the wiring. Without electrical grounding, this stray voltage could start a fire, damage appliances, or shock bystanders.

What is the difference between star and delta?

Star and Delta Connections are the two types of connections in a 3 – phase circuits. A Star Connection is a 4 – wire system and a Delta Connection is a 3 – wire system. Hence, most of the power generated and distributed is actually a 3 – phase power (but majority of households will receive a single phase supply).

What happens if the CT is grounded at multiple locations?

If the current transformers are grounded at multiple ground points, the normal current does not create any problem. However, during a fault condition, the magnitude of potential rise at the different ground points of the current transformer will be different.

Why the secondary of CT Cannot be kept open?

If the primary circuit has current flowing the secondary circuit should never be opened. This can cause very high voltages to occur due to the Ampere-Turns of the primary that start magnetizing the core. This results in the core being saturated through a large portion of the cycle.