Quality of supply management by means of interruption statistics and voltage quality measurements

Transcription

1 Quality of supply management by means of interruption statistics and voltage quality measurements Gerd H. Kjølle, Helge Seljeseth and Jørn Heggset, Frode Trengereid, Norwegian Water Resources and Energy Directorate 1

2 Introduction The paper focus on statistics of reliability of supply and voltage quality in Norway The documentation is an important basis for the quality of supply regulation and management Interruption recordings are standardized using the fault and interruption information tool FASIT Voltage quality measurements are based on IEC and CENELEC standards ( i.e. EN50160 etc) Interruption data presented for 6 years: Voltage quality data presented for the period

3 Quality of supply REGULATION in Norway The new Norwegian Energy Act from 1991 Mandatory reporting of interruptions > 3 min. from 1995 Revenue cap regulation of network companies from 1997 Quality dependent revenue caps from 2001: The Cost of Energy Not Supplied arrangement Further quality of supply regulations expected from 2004: Specific requirements for measurement of voltage phenomena? Minimum standards for the reliability of supply? 3

4 Key figures reported Number of interruptions per delivery point Annual duration per delivery point [hours] Duration per interruption [hours] ENS per Energy supplied [%] Interrupt-ion costs [million ] Total average per year 3,0 5,2 1,7 0,03 90 Average for notified interruptions 0,8 2,2 2,9 0,01 29 Average for non-notified interrupt-ions 2,2 3,0 1,3 0,

5 Energy not supplied % 0,05 0,045 0,04 0,035 0,03 0,025 0,02 0,015 0,01 0,005 0 ENS referred to energy supplied Total ENS Due to notified interr Due to non-notified interr

6 Interruptions in overhead vs cable networks, average Number or hours per year Annual number and duration of interruptions at the distribution level, Overhead network Cable network Number of interruptions Annual interruption duration 6

7 Main causes for energy not supplied Unknown/ not specified 32 % Distribution system Environmental 40 % Other 1 % Technical 22 % Human 5 % 7

8 NEW 2001/2001 survey in Norway on interuption and voltage quality costs NOTE! Preliminary results for residential customers only! Direct worth: Duration 1h: 2,4 Euro/kWh ENS Duration 2h: 2,4 Euro/kWh ENS Duration 4h: 2,3 Euro/kWh ENS Duration 8h: 2,1 Euro/kWh ENS Willingness to pay Duration 1h: 1,5 Euro/kWh ENS Duration 2h: 1,2 Euro/kWh ENS Duration 4h: 1,1 Euro/kWh ENS Duration 8h: 0,8 Euro/kWh ENS The TRUTH somewhere in between 8

9 Voltage Quality measurements Initially 43 PQ monitors in 1992 and close to 70 by the end of Database: 4,4 GB from 624 locations (~ files). All PQ parameters (EN50160) except flicker measured. Anonymous data to minimize data filtering risk. Possible to sort measurement locations by location parameters like % overhead line vs. cable, voltage level etc Database strength many locations, several years measured (number of PQ parameters) Database weakness Very varying measurement period, no flicker measurements 9

10 Examples of measurement results Flicker has not been reported as a significant problem in Norway except for in one region in northern Norway. This problem in Mo i Rana developed and got worse after measurement equipment was chosen in 1991/1992. The two main reasons for the increase of flicker in that specific region were: Considerable reduction in short circuit capacity in that region of the network due to the deregulation of the power market. (The operational pattern of the power stations is very dependent of the spot market price.) Permanent damage of the local SVC due to a fire. 10

11 Examples of measurement results - LEVELS Distr. 5 % level 50 % level 95 % level THD 0,52 % 1,4 % 3,8 % High V 5 % level 50 % level 95 % level THD 0,49 % 1,0 % 1,9 % High voltage Distribution 11

12 Examples of measurement results - CAUSES Low to moderate level of harmonics due to a high % of linear load One of the main reasons for a relatively large number of short interruptions in the Norwegian distribution network are the low number of arc suppression coils in the medium voltage overhead lines. Switching of capacitor banks without any mitigation against switching transients have caused many of the measured transients of moderate frequency. Synchronized switches on capacitor banks are not yet very common in Norway. 12

13 Examples of measurement results - TRENDS Slightly increased harmonics (Slightly increased flicker) signifficant increase in one location 13

14 OVERHEAD vs. CABLE NETWORK (Distribution network) The number of short interruptions, voltage dips and transient overvoltages are verified to be significant higher in overhead line networks compared to cable networks The higher number of short interruptions is strongly related to the low number of arc suppression coils in medium voltage overhead line networks in Norway. Short interruptions in overhead vs. cable networks: average of 19 vs. 6 per year Transient overvoltages in overhead vs. cable networks: 11 times more transients 2,4 times higher average magnitude. 14

15 CUSTOMER COMPLAINTS 15

16 Conclusions Results from 6 year of mandatory reporting of interruptions and 10 years of voltage quality measurements The reliability level in terms of ENS is slightly improving The voltage quality has shown no significant change, except for a moderate increase in harmonic voltages There is a relatively high number of short interruptions, mostly due to few installed arc suppression coils The data base of interruptions and voltage measurement is steadily improving These data and statistics are important as a basis for the quality of supply regulation and management in Norway 16

17 THANK YOU for your attention 17