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SHUNT CAPACITOR FUNDAMENTALS AND PROTECTION

OVERVIEW. (1) Introduction(2) Configurations(3) Design(4) Operation(5) Protection(6) Conclusions. INTRODUCTION. Shunt capacitor banks (SCB) are mainly installed to provide capacitive reactive compensation/power factor correction.They are installed near the load terminals, in factory substati

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SHUNT CAPACITOR FUNDAMENTALS AND PROTECTION

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    1. SHUNT CAPACITOR FUNDAMENTALS AND PROTECTION sandeep kerketta sandeep kerketta

    2. overview overview

    3. INTRODUCTION Shunt capacitor banks (SCB) are mainly installed to provide capacitive reactive compensation/power factor correction. They are installed near the load terminals, in factory substations, in the receiving substations to provide leading volt-ampere-reactive. By using shunt capacitors line drop is reduced and the voltage regulation is improved. They are switched in when kVA demand on the distribution system rises and voltage of bus drops.

    4. Disadvantages 1. proportional to the square of the voltage and consequently when the voltage is low and the system need them most, they are the least efficient.

    5. Fig 2. High voltage shunt capacitor

    6. THE CAPACITOR UNIT AND BANK CONFIGURATION The Capacitor Unit The capacitor unit, Fig. 3, is the building block of a shunt capacitor bank. The capacitor unit is made up of individual capacitor elements, arranged in parallel/ series connected groups, within a steel enclosure. The internal discharge device is a resistor that reduces the unit residual voltage to 50V or less in 5 min.

    7.

    8. The SCB of the line abosrbz leadind var (i.e generates lagging var). At the time of light load the lagging vars produced by the lines are much larger than that required by loads. These surplus lagging vars must be absorbeed by additional equipment to keep voltage profile within limits. SCB are those reactive power compensating equipment to generate generate or absorb vars.

    9. S=P+jQ Where, S=apparent power=VI(kva) Q=reactive power=VIsin?(kvar) P=active power=VIcos?(kw)

    10. Capacitor unit capabilities Relay protection of shunt capacitor banks requires some knowledge of the capabilities and limitations of the capacitor unit and associated electrical equipment including: individual capacitor unit, bank switching devices, fuses, voltage and current sensing devices. Capacitors are intended to be operated at or below their rated voltage and frequency as they are very sensitive to these values; the reactive power generated by a capacitor is proportional to both of them (kVar ˜ 2p f V2 ).

    14. 3.. Banks employing internally fused capacitor units are configured with fewer capacitor units in parallel and more series groups of units than are used in banks employing externally fused capacitor units

    16. The protection is based on the capacitor elements failing thus short- circuiting the group. When the capacitor element fails it welds and the capacitor unit remains in service. The voltage across the failed capacitor element is then shared among all the remaining capacitor element groups in the series.

    21. Grounded Wye-Connected Banks

    23. Ungrounded Wye-Connected Banks

    25. Delta-connected banks are generally used only at distributions voltages and are configured with a single series group of capacitors rated at line-to-line voltage. 2. With only one series group of units no overvoltage occurs across the remaining capacitor units from the isolation of a faulted capacitor unit.

    26. CAPACITOR BANK PROTECTION

    27. Capacitor Unbalance Protection

    28. 5. The unbalance protection should have minimum intentional delay in order to minimize the amount of damage to the bank in the event of external arcing.

    32. THANK YOU

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