Power Quality is a measure of how closely the power in an electrical system matches nominal (ideal) characteristics. It is common for actual electrical parameters to vary somewhat, but allowable ranges are typically very small. Good power quality means that the parameters are within acceptable limits for the electrical system. Poor power quality has excessive variations in the parameters, which can cause damage to loads and circuit equipment.

Power quality problems can be caused by the electrical generation and distribution equipment, but they can also be caused by loads operating within the electrical system. Power quality can involve many characteristics of the electrical supply, such as Voltage, harmonics, power factor and unbalanced conditions in the three-phase power supplies. These can all be monitored and conditioned if improvement is necessary.

Why Are we concerned about Power Quality?

The ultimate reason that we are interested in power quality is economic value. There are economic impacts on utilities, their customers and operators of load equipment.Modern customers use large number of sensitive devices comprising of power electronics that are quite sensitive to power quality disturbances in the supply network. From worldwide customer surveys, it is found that complaints on PQ related disturbances (for example: harmonics, voltage dips, flicker, etc.) are increasing every year.

It has been observed that the customer’s polluting loads often interact adversely with the network components and distort the network’s voltage. When the supply voltage is distorted, the customer’s device draws non-sinusoidal current from the network that might be different than the sinusoidal voltage condition. This can cause many technical problems (such as extra heating, mis-operation, early aging of the devices etc.) to the customer's devices at the point of installation. The non-sinusoidal current also causes extra losses and other problems to various network components (as example: cables and transformers). Moreover, poor PQ often has large financial consequences to the affected customers (mainly to the industries with process plants). In extreme cases, poor PQ of the electric supply can cause financial losses to the network operators and the equipment manufacturers too.

The below points highlight the typical Power Quality issues faced by industrial & commercial facilities and Energy Savers Power Quality optimisation solutions.

Energy Savers Power Quality ECM Solutions

Power Quality Audit

In order to understand the facilities existing Power Quality, Energy Savers conduct a Power Quality Audit of the Medium/Low Voltage network. Energy Savers skilled engineers and technicians measure and analyse the Power Quality on MDB/LV Room, as well as SMDB and load levels and develops an overall picture of the power quality (PQ) situation. Then we determine the most critical elements and the “lowest hanging fruit", which justify an investment. Where required, ES performs all elements and steps up to an Investment-Grade Power Quality Audit, which can be the basis for a short- / mid- or long-term investment and cost savings plan (ESM = Energy Cost Savings Measures).

Energy Savers have the most comprehensive audit data loggers and meters in the industry to diagnose the existing Power Quality and identify issues that are outside of acceptable international standards: EN50160 and IEC 61000

Voltage Optimization

  • Voltage Optimisation is a proven Energy Efficiency measure with more than 10,000 installations worldwide. It addresses three main issues:
    • Over/Under-Voltage Compensation
    • Voltage Stabilization
    • Phase Voltage Balancing (as part of a Load/Phase Balancing and PQ (Harm/Q Compensation)

Voltage Optimisation is a prime ESM (Energy Saving Measure) that can realise significant Cost Savings with a rapid ROI (Return on Investment), typically within less than 24 months from date of implementation, as it achieves direct and indirect savings:

  • Direct Savings: Reduction of waste electrical energy (not effectively usable by the End Loads)
  • Indirect Savings: Reduction of heat load from resistive conversion of the waste electrical energy

Our Voltage Optimisation solutions are specifically configured to address the Voltage and Power Quality conditions for each market and each client:

  • Made in Europe to our customer-specific configurations derived from Power Quality Audit (including 5-30 days Voltage audit), addressing incomer sizes of 100kVA -4500kVA LV Incomer sizes in 1PH, 3PH and 3PH+N configuration
  • Fully CE, TÜV and BSI certified and compliant to all relevant EN and local utility requirements – they deliver:
    • Over Voltage Reduction and Voltage Stabilization
    • Per-Phase Regulation and Compensation
    • Compensation can be remotely adjusted in real-time to any changes on load side
    • Compensation of Over Voltage, as well as Under Voltage (+/-10%)
    • Integration with existing Power Quality Equipment, BMS and EMS possible

Voltage Optimisation can realise energy savings of between 5-12%

Power Factor Correction

Power factor is the ratio between the kW and the kVA drawn by an electrical load where the kW is the actual load power and the kVA is the apparent load power.

Simply, it is a measure of how efficiently the load current is being converted into useful work output and more particularly is a good indicator of the effect of the load current on the efficiency of the supply system.

Improving the PF can maximize current-carrying capacity, improve voltage to equipment, reduce power losses, and lower electric bills. The simplest way to improve power factor is to add PF correction capacitors to the electrical system. PF correction capacitors act as reactive current generators. They help offset the non-working power used by inductive loads, thereby improving the power factor.

However, the interaction between PF capacitors and specialized equipment, such as variable speed drives, requires a well-designed system.Often, we find significant issues with existing CB/PFC installations. Such instances offer significant potential for incremental improvements and cost savings.

Today’s drive loads, specifically VFD and VSD (Variable Frequency Drives, Variable Speed Drives)-controlled drive, pump and automation loads need rapid supply of reactive power during start-up and standard operations. Due to the associated power electronics (inverters, rectifiers, AC/DC and DC/DC power supplies), these loads are producing significant amounts of current and voltage harmonics.

Traditional Capacitor Banks are not suited for such loads, as they are “too slow” (a contactor-switched capacitor step needs ca. 0.8 – 1.5 seconds for each step switch) and not protected against impact and accumulation of typical harmonic loads, such as 5th, 7th and 11th order. Further, for VFD Pump loads, it is essential to provide a per-Phase Reactive Power Compensation, specifically for start-up inrush mitigation, as this allows to balance out load imbalances, which will be otherwise further multiplied by harmonics load-related imbalance and resistive/waste heat de-rating of the VFD drive/pump equipment.

Energy Savers DPFC solution

The Dynamic Power Factor Compensator (DPFC) is a high performance power electronics system that responds instantly to changing reactive power requirements, while providing continuous compensation for harmonic loads. DPFC units can be built with active or passive harmonics compensation; for VFD-type loads detuned filter reactors are sufficient and more cost-efficient, as compared to active harmonics compensation.

DPFC units must be specifically configured in size/capacity, as they need to reflect the exact requirements of the MDB Panel, SMDB Panel, specific switch gear cabinet or load group, where the unit will be installed. Like standard Capacitor Banks, DPFC units are installed as compensation/injection units in parallel, either to MDB Panel internal bus bar, or as cabled connection of the switch gear cabinet. The location is either replacing an existing Capacitor Bank, or being installed downstream of an existing Capacitor Bank, providing the fast-changing peak reactive power loads (while the Capacitor Bank will in such case provide the “Reactive Base Load”) and protecting Capacitor Bank and the LV Switch Gear from the impact of harmonic distortions, by virtue of the integrated Detuned Filter Reactors.

The DPFC solution is further capable of correcting imbalance in a three-phase system network by injecting negative sequence kVar currents. This feature can be used to balance loads across all phases. Imbalance together with rectifier loads is particularly harmful, as it causes overloading of phases inside the rectifier and in extreme cases premature failure. Imbalance also increases heating inside direct online motors, reducing lifetime and lowering efficiency

Energy Savers DPFC is the most performant fast-switched/dynamic reactive power compensation solution available in the market. We can provide the solution in a variety of cabinet options, as standalone units, or integrated modules which can be integrated with other Power Quality solution modules, such as active/passive harmonics filters, voltage regulation/stabilization, soft starters, VFD drives and smart metering/control solution.

We can provide DPFC cabinet units with 3P capacities of 75kVAr – 525kVAr, or Single Phase capacities of 25kVAr – 300kVAr, allowing to build modular and distributed Reactive Power and Harmonics Compensation solutions, across multiple, inter-connected, or standalone DPFC, Harmonics Filter and Voltage Stabilization modules, allowing to address any Power Quality requirements.

We offer DPFC solutions for LV grids/loads in 240VAC/1P, 400VAC/3P and 690VAC/3P, as well as for MV grids/loads in 3.3kV, 6.6kV, up to 30kV, as part of integrated SVC compensation/filter circuit and/or STATCOM units.  Here some examples of customized LV DPFC units

Harmonics

Harmonic Waveform Distortions, often simply referred to as harmonics, are an increasing challenge and hence an important aspect for any Power Quality Optimisation effort.

Total harmonic distortion (THD) is the cumulative degree of distortion within an electrical current compared to the ideal. Most household electrical systems draw linear loads. On a linear current sine curve, the peaks and troughs are smooth, even, and sinusoidal. Some distortion can take effect in residential circuits but not enough to cause significant efficiency issues. However, many industrial and commercial applications use non-linear loads. The way generators, converters, and power supplies draw power introduces a degree of harmonic distortion (the result of combining multiple waves of varying frequency) that can seriously affect a power system’s efficiency.

Typical Non-Linear loads

  • Adjustable speed drives (ASDs), Variable Speed Drives (VSDs), Variable Frequency Drives (VFDs), SCR drives
  • AC motor drives (AC/DC/AC) and DC motor drives (AC/DC)
  • Three-phase full wave rectifiers and wave/phase converters
  • Six-pulse converters (many meters, sensor-driven drives etc.)

Harmonics can generate significant issues for the utilities and all users of electrical energy:

  • create or facilitate resonance events, which can be damaging and even fatal
  • reduce electrical systems and end load efficiency and life-time
  • increase energy waste / losses directly and indirectly
  • increase energy costs by up to 20%

Over time, the harmonic distortion can negatively affect electrical equipment and lead to degradation of individual components. Increased current leads to excessive heat and interference with over-the-wire communications. Both of which, if left unchecked, can cause long term damage to not just electrical equipment but entire electric systems as well.

Energy Savers Harmonic Compensation Solution

Harmonics compensation or reduction is rapidly becoming an important aspect of Power Quality Optimisation. Energy Savers tackles the “Harmonics Compensation challenge “ and the Harmonics Distortions found in many electrical networks. Our solutions may include:

  • Passive and Active Filters and PQ Optimisation unitsIntegrated Harmonics Compensation Solutions
  • Harmonics Compensation Module/Upgrades for PFC/Capacitor Bank Installations
  • One important technical aspect of harmonics are the ferro-resonance events which can be triggered by harmonics distortions and cause mechanical wear and electrical as well as mechanical failure.
  • The commercial impact of Harmonic Distortions is significant, and costs of issues caused by harmonics are growing continuously

Harmonics, above a certain threshold (utilities cite a 3% or 5% threshold for Total Harmonic Distortion (THDi), but frankly today we see 3th, 5th, 7th and 11th current and voltage harmonics percentages of >15% in many commercial& Industrial assets) can have a significant negative impact on many loads and the stability of an entire electrical system.

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