Upload
georgia-mcdowell
View
212
Download
0
Tags:
Embed Size (px)
Citation preview
1F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
POWER FACTOR CORRECTION WITHIN INDUSTRIAL SITES
EXPERIENCES REGARDING PQ AND EMC
IBERDROLA DISTRIBUCIÓN ELÉCTRICAF. Ferrandis
2F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Industrial Compensation vs Distribution Network Compensation
• Common practice both in distribution networks and industrial facilities...
• ... But different reasons...
• Utilities: Technical (system capacity, efficiency, voltage drops), economic (line losses, infrastructure costs)
• Customers: Avoid penalties, existing space
3F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Industrial Compensation vs Distribution Network Compensation
• ... And also different problems...
• Utilities: Tipically maintenance problems (capacitors & circuit breakers)
• Customers: Serious problems caused by their own capacitor banks– Harmonics– Others:
• voltage variations; interharmonics; high frequency surges; EMC problems
4F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Customer facilities: problems in reactive power compensation at MV/HV• Might be the cheapest for Q > 1 MVAr• Usually:
– Without regulation– Always connected– Connection through fuses (no circuit breakers)
• Predominantly reactive system very little damping higher resonance at high order frequency
• Two common configurations:– Capacitor banks connected directly at the PCC– HV customers with capacitor banks connected at
MV busbars
5F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Customer facilities: problems in reactive power compensation at MV/HV
• Harmonics can affect the whole system• More complex behaviour, considering the whole
distribution network• Problems:
– Different configurations Variable resonances problems with harmonics (itself & other sources)
– Switching of single capacitor banks without limiting inductances discharges onto substation capacitor bank stressed circuit breakers, damages
...at the PCC...
6F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Customer facilities: problems in reactive power compensation at MV/HV
• LC system with very low damping• Bigger capacitor banks and non-linear loads
(compared with MV public grids)• Problems:
– Untuned: very strong connection transients– Tuned: attraction of harmonics from the network
• Arc furnaces: L-C filters overload due to interharmonics
– Both: resonance variation due to capacitor installations without further studies
...at MV busbars...
7F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Customer facilities: problems in reactive power compensation at LV
• Most frequent, commercial products up to 1000 kVAr– Standardised, untuned (1.3·Inominal)– Oversized, untuned (1.5·Inominal)– Tuned (with reactors)
• Commonly automatic banks– High number of switching operations – Multiple configurations
• When loads with PF < 0.7 larger capacitor banks compared with Stranformer low frequency resonance
• Great % disturbing loads harmonic currents increase• Summation laws for harmonics: worse than in MV grids
8F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Customer facilities: problems in reactive power compensation at LV
• Problems in capacitor banks:– overloads due to harmonics in untuned capacitor
banks:• by a resonance• circulation of high order harmonics
– disturbing loads with good PF (e.g. non controlled rectifiers)
– coexisting tuned & untuned capacitor banks
– high temperature in tuned capacitor banks due to inductance losses
– stressed contactors
9F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Customer facilities: problems in reactive power compensation at LV
• Problems in other equipment units:– control or switching failures due to harmonics– transformer overheating: resonance, harmonic
currents– EMC: control system failures due to radiated fields
10F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Customer facilities: problems in reactive power compensation at LV
CASE STUDY 1: OVERHEATING PROBLEMS IN MV/LV TRANSFORMER
• After installing a 3rd. order filter to reduce harmonic content 20ºC decrease in transformer!!!
Before: After:
Problems in other equipment units:
11F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Customer facilities: problems in reactive power compensation at MV/HV
CASE STUDY 2: EFFECT ON THE NETWORK IMPEDANCE
...at the PCC...
0,001
0,01
0,1
1
10
100
1000
10000
0 5 10 15 20 25 30Harmonic order
Impe
danc
e (o
hms)
Network configuration 1
Network configuration 2Network configuration 3
• 30 kV customer with 2 MVAr, usually feeded from near substation (Scc=1000 MVA, Q=14 MVAr)
• Problems (23th harmonic resonance) appeared with auxiliar feeder (Scc=200MVA, Q=0)
• Different grid configurations different resonances No control over the final situation
12F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Customer facilities: problems in reactive power compensation at MV/HV
CASE STUDY 3: OVERLOAD OF AN ARC FURNACE WITH L-C FILTER
...at MV busbars...
• Arc furnaces emit interharmonics during initial melting overload of capacitor bank components
• L-C filters must be oversized• Dumped filters recommended
13F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Conclusions (I)
• Similar approach: Industrial customers and utilities use capacitor banks to correct PF
• ... but different problems arise– Utilities: mainly switching problems– Customers: harmonic resonances and others
(interharmonics, high frequency surges, EMC problems)
• Several reasons:– HV/MV: Harmonics can affect the whole system. Complex
behaviour due to changes in the network impedance
– LV: High rate Qcapacitor bank / Stransformer,, poor PF loads, Great % disturbing loads, different summation laws
14F. Ferrandis_SP_ALPHA 2_BLOCK 2_Paper 35_Presentation
Barcelona 12-15 May 2003
Conclusions (II)
• Solutions in industrial sites:– Transient switching overcurrent Transient limitation
• MV: capacitor banks with reactors
• LV: usually adapted contactors, occasionally static switches
– Capacitor overload Harmonic current limitation or capacitor oversizing
• MV & LV: tuned capacitor banks or capacitors of oversized nominal voltage
– Harmonic voltage reduction Filtering• MV: pasive filters (L-C or dumped)
• LV: usually pasive filters, ocassionally active filters