Considering that in 2000 the total annual Hydro-Québec distribution electrical consumption was 150TWh, the following table presents the percentage of energy losses caused by harmonics.
Table B.7- Estimated distribution system power losses produced by harmonics in percent of total energy used
Harmonics level of 50%
IEC Harmonics level of 100%
IEC Harmonics level of 150%
IEC
LV Line 0.018 0.072 0.162
MV Line 0.014 0.054 0.122
Transformer 0.006 0.023 0.051
Capacitor 0.001 0.003 0.007
Total 0.038 0.152 0.343 At the time of the study, the harmonics level of Hydro-Quebec’s distribution network was evaluated at near the 50% IEC planning level. This represents a 0.038 percent of losses caused by harmonics. For comparison, a similar study [166], done over the Greek MV and LV distribution network, gives values in the range of 0.15% to 0.20%, which is more like a harmonics level of 100% IEC level of the Hydro-Québec study. In Greek publication, simplifications and assumptions were made in order to obtain an over estimation of the economical impact of harmonics in the distribution network. The aim was to conclude that it is useless to put effort in network harmonics improvement. Both results could not be directly compared in term of network configuration, equipment characteristics, harmonics level, technique used and assumptions made, but they are quite similar.
(Losses) = (Harmonics)2
50% 100% 150%
IEC threshold
losses
% harm
P = R x I
2APPENDIX 4
A Structuring the Data Collection Process
For the purpose of structuring the data collection process, a proper taxonomy can be useful; in the following the most important items are recalled and described.
Critical sectors
They are in general PQ critical and demonstrate similar PQ sector sensitivity, for which the methodology can be potentially targeted.
CS1. Industrial sectors type uni-product / uni-process (continuous manufacturing) 1. Food / Beverage (production processing and preserving, NACE25 15) 2. Glass, ceramics, cement, lime and stone (NACE 26)
3. Metallurgy (NACE 27) 4. Pharmaceutical ( NACE 24.4) 5. Plastic and rubber (NACE 25)
6. Publishing, printing and reproduction of recorded media (NACE 22) 7. Pulp and Paper industry ( NACE 21)
8. Refineries, chemical industry (NACE 23.2, 24 except 24.4) 9. Semiconductor industry (NACE 32.1)
10. Textile (particularly preparation, spinning and manufacture NACE 17.1 and 17.5)
11. Wood and wood products (particularly production of sheets, boards and panels NACE 20.2) CS2. Industrial sectors type multi-product / multi-process
1. Automotive industry (NACE 34)
2. Continuous or highly automated or precision manufacturing – not defined in other sectors - metal products (NACE: 28 fabricate metal products - except structure work 28.1 , 30 - office equipment, 31- electrical equipment, 32 – except 32.1 – RTV and telephony electronics, 33 – medical equipment)
3. Manufacture of machinery (NACE 29 and 31) CS3 Services sectors
1. Air transport (NACE2 62)
2. Database activities e.g. hosting services (NACE 72.4)
3. Financial intermediation (particularly central banking, but also other general transactions, section J; NACE 65-67)
4. Hospitals (NACE 85.1) 5. Hotels (NACE 55.1) 6. Railways (NACE 60.1)
7. Telecommunications (NACE 64.2) Cost categories
1. Process interruptions 2. Process slowdown 3. Equipment damage
4. Reduced lifetime and mis-operation (postponed costs) 5. Reduced energy efficiency - increased energy loss
25The NACE Code is a pan-European classification system which groups organisations according to their business activities;
http://ec.europa.eu/comm/competition/mergers/cases/index/nace_all.html
6. Product quality 7. Worker productivity 8. Other indirect costs
Cost types - Operating consequences
1. WIP loss, often referred to as production loss or production damage. This category includes this part of labor and material costs which has been inevitably lost. This category has two major components - labor and material cost.
2. Working capacity loss – basically quantifies efforts to make up this part of production which can still be repaired or reused – WIP recovery
3. Labor cost resulting from production outage – lost or extra paid
4. Other related costs when quantification using above mentioned categories is not easily possible.
These could be a process slow down when it cannot reach its nominal efficiency including process restart cost and additional maintenance costs. These include process and process restart cost.
5. Equipment related costs, including equipment damage and replacement costs, hire of temporary equipment, and running costs of back up equipment
6. Indirect costs, e.g. consequences of late delivery such as penalties to clients, extra compensation to personnel, cost of personnel or equipment evacuation, extra insurance cost
7. Savings from unused resources (labor, energy, material).
PQ phenomena
1. Voltage dips and short interruptions 2. Harmonics (current and voltage) 3. Surges and transients
4. Flicker 5. Unbalance 6. Earthing and EMC Equipment:
as a PQ source and affected by PQ 1. Capacitors
2. Contacts and relays 3. Electric motors 4. Electronic equipment 5. Lighting equipment 6. Processing equipment
7. UPS uninterruptible power supplies 8. VSD and other static converters 9. Welding and smelting equipment PQ consequences
1. Circuit breakers (including protective devices) nuisance tripping 2. Capacitor damage
3. Capacitors – dielectric loss 4. Computer lock up
5. Computers / other electronics damaged 6. Data loss
7. Electric shock 8. Lights flicker or dim
9. Loss of synchronization of processing equipment 10. Motors / process equipment - malfunction or damage 11. Motors overheating – energy losses
12. Noise interference to telecom lines 13. Relays /contactors nuisance tripping
14. Transformers / cables overheating with related energy losses 15. Premature ageing and loss of reliability of electrical equipment
16. Overheating of neutral conductor in lines and transformers and related problems (e.g. transient overvoltage, tripping of RCDs, losses)
Solutions
1. Equipment immunity 2. Backup generator 3. Dynamic voltage restorers 4. Harmonic filter
5. Isolation transformers
6. Line conditioners or active filters 7. Multiple independent feeder 8. Oversizing equipment 9. Shielding and grounding
10. Site generation capable of substituting supply 11. Static transfer switches
12. Static VAR compensator
13. Surge protectors on key pieces of equipment 14. Uninterruptible power supply (UPS) devices 15. Voltage stabilizers
B Executing Data Collection Process – End User Perspective
With reference to the Model A presented in Chapter 4, the following step-by-step procedure can be recommended to estimate the process interruption cost, PIC:
• Step 1: Based on the assumptions mentioned above, evaluate the total number of product variants, the total number of process activities at any given instant and the maximum number of potential failures among all process activities.
• Step 2: For each product variant, determine the associated progressive cost components from A1 to A726 for each process activity. Note: If for a particular process activity the maximum number of failure scenarios is less than the maximum number of failure scenarios in all process activities, then the cost components A2, A3, A4 and A5 associated with failure scenarios assumes zero value.
Establish the cost related to component A6, particularly employees tolerance for each failure instance of process activity. Establish customer satisfaction and reputation retained level for instance of non-delivery of a product variant in time. Finally calculate savings A7 due to failure scenarios.
• Step 3: Prepare a work schedule highlighting the active process activities for a typical day for which process interruption cost profile has to be established. This work schedule should include process activities for various product variants and their simultaneous.
The proposed specification and division of sectors by Taxonomy A may help an end user to focus economic data collection on certain aspects.
The proposed methodology suits the collection of cost data in ‘industrial - uni-process’ sectors. Most of processes are organized in a series topology as indicated in the Figure B.1. With reference to Fig.B.1, the stream I is the simple extreme. In such a case, close attention should be paid to the calculation of process interruption costs as all the processes are closely interdependent. In a ‘Just in time’ scenario, where there are no buffers in the process, one process failure may stop the whole production line.
These sectors are particularly vulnerable to voltage dips and related process interruptions
For sectors classified as ‘Industrial - multi-process’, the production process is less often performed in continuous stream – Figure B.1 – stream VI, as an extreme. In such case one process interruption may not
26Chapter 4 clause 4.3.2
necessarily stop other processes. The consequences are limited to the critical processes which are needed to make up for lost lead time of the final product. The focus is therefore on extra cost (e.g. bonus extra time labor cost) to recover lost or partly lost WIP (A127).
These sectors are vulnerable to voltage dips but also other phenomena like harmonics and unbalance, transient and surges.
Figure B.1: Six typical configurations considered for industrial processes
In the ‘Services’ sectors it can be difficult to distinguish the root cause of process interruption, particularly in a commercial environment where software, hardware or a PQ issue maybe responsible.
Once the root cause has been attributed to PQ, the consequences could be:
• Loss of transactions in progress requiring data recovery, reprocessing and repeated transmission. The standard data collection process described here should be modified either using a mix of A1, A2 and A5 cost components.
• Process restart cost using A4 cost calculation
• Other costs, particularly lost revenues (missed opportunities) as result of customer dissatisfaction and loss of reputation, but also such consequences as penalties and other elements of A5 cost component.
• Potential savings from A7 are usually negligible.
The alternative to the procedure described above is to use A3, the process slow down method, to simply calculate business slow down rate.
In addition, due to lack of clear differentiation whether a process was interrupted or not, all phenomena related cost components should be used to check that nothing has been omitted. It also should be checked whether any items have been double counted, particularly A5 (equipment damage due to process
interruption) and equipment damage due to occurrence of PQ disturbance.
Service sectors are relatively more vulnerable to the consequences of long interruptions but PQ may still be the root cause of substantial economic losses.
C Conclusions
Deregulation and industry restructuring are placing utilities under increasing pressure to both improve customer reliability and decrease cost. To remain competitive, it is critical to prioritize maintenance tasks so that the best possible reliability is achieved with increasingly constrained maintenance budgets.
27Chapter 4, clause 4.3.2
I II
III
IV
V
VI
The purpose of maintenance is to extend equipment lifetime and/or reduce the probability of failure.
Corrective maintenance replaces or repairs failed components, while preventive maintenance is a proactive effort to improve the condition of an unfailed component that may be deteriorated to some degree.
Power quality can be surveyed for three major purposes:
1. Technical reasons (which are more important in industrial centers and to facility managers) 2. Economic reasons (including all sectors linked with the electrical system)
3. Social reasons (in which the governmental system is bound to offer desirable services) Appropriate quality of electrical energy can greatly reduce expenses arising from losses or system disturbances. Improvement of power quality can overcome these problems as well as increase equipment longevity and system reliability.
In poor power quality, financial damages imposing upon residential, industrial, and trade consumption would be very different. Therefore, it must not be neglected that some huge portion of electrical energy is consumed in residential utilization. Losses of power, decline in useful life of power system equipment, as well as non-purchased energies due to power quality deficit are counted as parts of financial damages imposed upon facility managers. Furthermore, governments fulfill community satisfaction and demands with legislation for facility managers. All the above-mentioned instances appear as positive pressure in promotion of power quality in a power system.
The scientific response is that they are only due to economic limitations, which of course the alternative implication may be suffering from poor initiatives in establishment of state laws in this respect and also lacking practical scientific capability necessitated in supplying those wants.
In this report, attempts have been made toward implicating economic damages resulting from quality problems encountered with shape of consumption. Requirement investment for power quality promotion counts as main criteria for comparison.
APPENDIX 5
A Illustrative Case Study
This section illustrates the application of the NPV approach to a hypothetical high-tech facility based on an actual facility. The example considers a semiconductor wafer-fabrication factory located in the United States. Wafer fabrication requires a high level of power quality and reliability due to the sensitivity of the equipment and process controls and therefore is a strong candidate for applying the NPV analysis.