Presentation on “Power Quality” Mr. P B Tupe

Presentation Sections What is Power Quality? Why Monitor Power Quality? Power Quality components European Standard EN50160 IEC 61000 Standard What should we demand from a PQM?

Steady-state disturbance What is Power Quality? Steady-state disturbance Transient disturbance

What is Power Quality? IEEE ..the concept of powering and grounding sensitive electronic equipment in a manner suitable for the equipment LPQI (Leonardo Power Quality Initiative) ..a supply that is always available, always within voltage and frequency tolerance, with a pure, noise free, sinusoidal wave shape Sankaran (modified) ..a set of boundaries that allow electrical appliances and systems to function as intended without significant loss of lifetime or performance In our first Annual Group Management Meet in 1999 we had showed a set of two slides, the first showing what we called our “Existing Objectives” and the second what we had identified as our future Challenges. Our existing objectives, we had then said, are to improve our performance, to create value for our shareholders, to become a world-class player, to be No 1 or No 2 in the market and to be market-oriented. If you think about it, these are a compact, inter-related set of objectives which had emerged out of our past performance.

A Brief History of Power Quality… 1879 1891 1917 1948 2006 First report on flicker Thomas Alva Edison invents the light bulb Jonas Wenström invents the three- phase system Shockley, Bardeen and Brittain invents the first transistor Increased use of power electronics Mostly linear loads Increase in non-linear loads The most severe power quality problems started to appear at the beginning of the 1950’s. This was due to the development of transistors which lead to non-linear loads in the power network. Computers, printers, and all other power electronic products represent non-linear loads.

Why Monitor Power Quality? The Cost of (poor) Power Quality: Production losses Extended outage time Shortened equipment lifetime e.g. Transformer Unexpected early failure Overloading of equipment Potential catastrophic failure Chain reaction In our first Annual Group Management Meet in 1999 we had showed a set of two slides, the first showing what we called our “Existing Objectives” and the second what we had identified as our future Challenges. Our existing objectives, we had then said, are to improve our performance, to create value for our shareholders, to become a world-class player, to be No 1 or No 2 in the market and to be market-oriented. If you think about it, these are a compact, inter-related set of objectives which had emerged out of our past performance.

Why Monitor Power Quality? According to a study performed by European Copper Institute in 2001, covering 1,400 sites in 8 countries, any given site in Europe has a 5-20 % probability that it will suffer from one or more of the problems listed. Typically, half of sites in energy-intensive industries or mission-critical office buildings will suffer from two or more problems In our first Annual Group Management Meet in 1999 we had showed a set of two slides, the first showing what we called our “Existing Objectives” and the second what we had identified as our future Challenges. Our existing objectives, we had then said, are to improve our performance, to create value for our shareholders, to become a world-class player, to be No 1 or No 2 in the market and to be market-oriented. If you think about it, these are a compact, inter-related set of objectives which had emerged out of our past performance.

Why Monitor Power Quality? Estimation of annual cost of poor PQ in Europe 10 billion EUR Power quality problems have increased since 2001 due to more sensitive equipment and more non-linear loads. Typical losses in some industries due to poor PQ (2001) Semiconductor production EUR 3 800 000 Financial trading (per hr!) EUR 6 000 000 Computer centre EUR 750 000 Telecommunications (per min!) EUR 30 000 Steel works EUR 350 000 Glass industry EUR 250 000 Ref : Copper Development Association’s booklet 2001

Power Factor Description / Causes: Phase angle between voltage and current. Caused by capacitive or inductive loads such as: Motors Long power lines. Consequences: Costs: Inefficient use of grid Overheating Losses Network must be designed for higher currents

Supply voltage variations Description / Causes: Slow variations in the RMS. Caused by: Changing loads Tap changes on transformers Consequences: Costs: Reduced life time of equipment Production losses Damage to equipment Production losses Reduced life time of equipment

Harmonics Description / Causes: Non-linear loads cause distorsion that causes other (higher) frequencies in the network. Caused by: Switched power supplies (computers), Power electronics, Motor drives Consequences: Costs: Increased losses. Overheating of neutral conductor and transformers Resonance phenomena resulting in high currents and voltages. Broken capacitor banks. Malfunction in control equipment Production losses Reduced life span of the equipment Increased investments in filters and compensating equipment

Flicker Description / Causes: Cyclic variations in the voltage RMS. Variations in the range 0-30 Hz. Caused by: Welding equipment Rolling mills Arc-furnaces Consequences: Costs: Blinking lights that irritate and tire the eye and cause headaches Indirect costs like reduced productivity Often expensive solutions

Voltage unbalance Description / Causes: Amplitude and/or phase varies between the three phases. Caused by: Uneven distribution of single-phase loads Trains Consequences: Costs: Loss of efficiency in 3 Ph motors Corrosion and increased current in neutral conductors. Stray currents in grounding system Reduced life span of the equipment Motor power cannot be fully utilised

Transients Description / Causes: Rapid and short (sub-cycle) changes in the voltage or current waveforms. Caused by: Lightning Faults and switching in the grid Start of engines Consequences: Costs: Tripping of protective equipment Faults/damages in electronics such as computers or control systems for machines Production loss Failure or damage to equipment Loss of information (computers)

Sags (dips) / Swells Description / Causes: Short variations in voltage RMS. Caused by: Lightning Faults and switching in the grid Start of engines, rolling mills, welding sets Consequences: Flicker Disturbances in electronic equipment such as computers or control systems for machinery Swells can destroy equipment (overvoltages) Costs: Production losses Loss of information in computers

Rapid Voltage Changes Description / Causes: Fast but small (<10%) variations in the voltage RMS. Caused by: Connection/disconnection of loads Tap changes on transformers Consequences: Flicker Costs: Indirect costs such as reduced productivity

Power (Poor) Quality In our first Annual Group Management Meet in 1999 we had showed a set of two slides, the first showing what we called our “Existing Objectives” and the second what we had identified as our future Challenges. Our existing objectives, we had then said, are to improve our performance, to create value for our shareholders, to become a world-class player, to be No 1 or No 2 in the market and to be market-oriented. If you think about it, these are a compact, inter-related set of objectives which had emerged out of our past performance.

Two categories of PQ standards Voltage characteristics standards EN 50 160 (EU standard) IEC 61000-2-2 (LV), -12 (MV) Norma Peruana (Peru) Victorian Distribution Code (Australia) Philippine Grid Code Venezuelan Grid Code Chinese standards Measurement methods standards IEC 61000-4-7 (harmonics) IEC 61000-4-15 (flicker) IEC 61000-4-30 (methods)

Voltage characteristics for electricity supplied by European Standard EN50160 Voltage characteristics for electricity supplied by public distribution systems Main characteristics of voltage at customer’s supply terminals Public low-voltage and medium-voltage networks Describes what is expected under normal operating conditions

EN50160 - Voltage variations Voltage magnitude: 95% of the 10-minute averages during one week shall be within 10% of the declared voltage of 230 V. All values shall be between -15% and +10%. Frequency: 99.5% of the 10-second averages during one year shall be between 49.5 and 50.5 Hz. The frequency shall be between 47 and 52% for 100% of the time. Voltage unbalance: 95% of the 10-minute averages during one week shall be less than 0.02. Voltage fluctuations: 95% of the 2-hour long-term flicker severity values during one week shall not exceed 1.0.

EN50160 - Voltage variations (2) Voltage harmonics: 95% of the 10-minute averages during one week shall not exceed the values given in the table below Note: As for all other characteristics these values hold for 99.9% of the locations during 95% of time

European Standard EN50160 – in short

Describes measurement methods which will give IEC 61000-4-30 Scope Describes measurement methods which will give reliable, repeatable and comparable results - regardless of the instrument being used Focused on parameters causing conducted phenomena Describes measurement methods – not thresholds or limits

IEC 61000-4-30 PQ Parameters Detailed specification of measurement methods and accuracy for: Power frequency Voltage RMS Flicker Harmonics and interharmonics Unbalance Dips, swells, interruptions and transients Mains Signalling

IEC 61000-4-30 Class A – Normative High accuracy Standards compliant Contractual verification Comparable results Class B – Indicative Lower accuracy May not meet all standards Demand analysis Results vary with instrument

IEC 61000-4-30 Flagging Concept When a single event such as a voltage DIP etc. occurs, the actual measurement interval shall be flagged and other parameters should be discarded during that interval to avoid counting the event more than once. New method !

Voltage RMS value The RMS value is calculated from every 10-cycle value without time gaps. Other measurement intervals can be calculated based on 10-cycle values. Accuracy 0.1% of nominal voltage. T

½ Cycle RMS values = 10ms (for DIPS detection) Performance specification, not a design specification ! ½ Cycle RMS values = 10ms (for DIPS detection) Measurement Aggregation time interval: 10 Cycles = 200ms 150 Cycles = 3s 10min Values are calc from 10 cycle values 2Hr Value = aggregated from 12 x 10min values In our first Annual Group Management Meet in 1999 we had showed a set of two slides, the first showing what we called our “Existing Objectives” and the second what we had identified as our future Challenges. Our existing objectives, we had then said, are to improve our performance, to create value for our shareholders, to become a world-class player, to be No 1 or No 2 in the market and to be market-oriented. If you think about it, these are a compact, inter-related set of objectives which had emerged out of our past performance. Class A devices - tested thoroughly as per guidelines Class B devices – Liberty to manf to specify the methods and accuracies Results of 2 Class A devices an be compared.

Sliding reference Nominal levels might vary over time, especially on medium and high voltage. Threshold values must therefore always follow the actual reference level. This is called sliding reference since reference level is always average voltage last minute. Sliding Reference

IEC 61000-4-30 Summary IEC 61000-4-30 provides standardised measurement methods IEC 61000-4-30 guarantees comparable results between normative instruments IEC 61000-4-30 guarantees users to have full knowledge about the instrument performance IEC 61000-4-30 helps manufacturers of PQ instruments to implement standardised methods and algorithms IEC 61000-4-30 is an essential document when developing new PQ standards

What should we demand from a power quality monitoring system? Accurate and reliable measurement Measure both voltage and current for disturbance tracking IEC 61000-4-30 Class A instrument Combination of permanent and portable instruments for full control of the whole network Portable unit suitable for field use: IP65 Designed for power quality monitoring: Remote communication solutions for both permanent and portable instruments Automated features: user defined limits, alarms etc Give statistical information: data stored for years, not just months

Reference IEC/ EN Standards Web sites / Product catlogues – Unipower ,Yokogawa, Fluke, GE, Areva, a-eberle, Megger, ABB, Siemens etc. www. Lpqi.com (Leonardo Power Quality Initiative) Copper Development Association’s Reports