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LV Anti-Resonant and Filtering Automatic Capacitor Banks

Main Lugs and Main Breaker Class 5860

Anti-Resonant and Harmonic Filtering Automatic Switched
Capacitor Banks

Reactivar^® AV6000 anti-resonant and AV7000 harmonic filtering auto-matic switched capacitor banks are specifically designed for networks containing harmonic energies which would otherwise damage standard fixed or automatic capacitor banks.

The problem: Harmonics are a natural by-product of non-linear loads such as variable frequency drives, motor soft starters, welders, uninterruptable power supplies, robotics, PLCs and other electronic devices. Harmonics introduce higher-than-60 Hz currents and voltages into the electrical distribution system. Capacitors are a low impedance path for these higher frequency components and thus will absorb these harmonic energies. Combinations of capacitors and system inductances (motors and transformers) can form series and parallel tuned circuits which can resonate at certain frequencies. The harmonics produced by non-linear loads can excite a standard capacitor bank into resonance. The resonance can magnify currents and voltages, causing system wide damage and equipment failure. This problem is growing in prevalence.

The AV6000 anti-resonance capacitor bank's primary function is power factor correction. Iron core reactors are added in series with the capacitor modules. The 3 phase reactors are custom designed and manufactured at our factory under tight tolerance specifically for the AV6000. The reactors tune the bank below the first dominant harmonic (usually the 5th, or 300 Hz). Below the tuning point, the system appears capacitive and thus corrects power factor. Above the tuning point, the system appears Inductive and thus resonance is minimized. The AV6000 design has the added advantage of removing up to 50% of the 5th harmonic to reduce overall voltage distortion.

The need for an AV7000 is usually determined by a power quality specialist. Although the AV7000 looks identical to the AV6000, its primary function is harmonic mitigation, with power factor correction being a secondary benefit. The distinction between an AV6000 and an AV7000 is the tuning point. By definition, if the tuning point of the capacitor/reactor combination is within ±10% of the target harmonic it is intended to absorb, it is referred to as a filter. If the tuning point is outside the ±10% limit, it is referred to as an anti-resonant system. As the tuning point of the system approaches the target harmonic, its effectiveness at absorbing increases. Hence, the need to classify its functionality. The PQc group should always be consulted prior to recommending it to customers.

A single remote Current Transformer must be located on the bus/cable at the main service entrance terminal compartment. CT sold separately. Refer to CT Selection Guide on page 4-26.

It is imperative to ensure that no other capacitors (fixed or automatic) are connected to the same network as the AV6000 or AV7000 capacitor banks. The components within these banks are carefully chosen to avoid network resonance between the substation transformer and the capacitor elements. Additional capacitors on the network will alter the characteristics of the AV6000, possibly leading to network resonance. The application of this product may warrant special consideration, please supply end customer telephone number and contact name when placing order.

The Square D Power Quality Correction Group provides engineering assistance for the application of capacitors in harmonic rich environments. Specialists at Square D can assess the likelihood of application problems and arrange for more detailed study if required. Solutions can include computer modeling and system simulation. Depending on the network, the solution may include de-tuned banks (AV6000) or fully filtered banks (AV7000). Our application engineers can make all the arrangements for system studies, custom engineering, installation and commissioning, as required by the application.

Modularized construction: Units are free standing, modularized "MCC style" in ASA 49 gray. Sections are ganged together as required with a maximum 300 kVAR per section at 480 V. Key operated latching is standard. Units are NEMA Type 1 standard, with NEMA Type 3R available upon request (NEMA Type 12 is not available). Top entry, main lugs or main breaker is standard. Bottom entry is optional.

Robust design: Capacitor modules are designed with higher than standard voltage and current ratings to provide long life on systems with high harmonic energies. Reactors are designed to operate at 115° C rise over a maximum 40° C ambient.

Advanced Safety Features: In addition to the standard safety features designed into the AV4000/5000 systems, the Reactors in the AV6000 have an embedded thermistor temperature detector. The stage will shut down and annunciate if the reactor should overheat, usually a result of excessive harmonic energies.