Pagpahimulos sa mga Outdoor Vacuum Circuit Breakers Sa Simulado nga mga Kalibutan
Ang mga outdoor vacuum circuit breakers kasagaran gigamit sa segmento sa Medium High Voltage (MHV). Sila usa ka importante nga komponente sa sector sa distribution, lalo na sa 11kV ug 33kV grids. Usa ka sarihana nga composite materials ang gigamit sa pagbuhat niining mga breakers. Sa dihang mahimong makita, ang vacuum interrupter ang labing importante nga komponente. Para sa mga outdoor circuit breakers, ang vacuum interrupter kasagaran gipakita sa usa ka porcelain housing.
Ang mga breakers mao ang gikonekta sa operating mechanism pinaagi sa fibreglass - reinforced resin - cast operating rods, nga sa ilang bahin gipakigkonekta sa usa ka common gang operating rod gihimo sa metal - steel. Ang operating mechanism sa mga outdoor vacuum circuit breakers kasagaran nagpadayon sa spring - type design, nga nahimutang sa usa ka sheet steel enclosure. Tungod sa paggamit og daghan nga materyales, importante nga i-assess ang compatibility sa mga materyales, sama sa design ug workmanship, sa daghang environmental conditions diin ang mga breakers intended to operate. Kini nga pag-assess nag-ensure sa trouble-free performance ug, isip resulta, ang stability sa electrical network diin sila anaa.
Ang environmental tests para sa mga circuit breakers, partikular ang low - temperature ug high - temperature tests, gi-cover sa clause 6.101.3 sa IEC 62271 - 100[1]. Para sa cold - volt climates, ang preferred temperature range alang sa minimum ug maximum values mao ang - 50°C hangtod + 40°C, tungod kay para sa very hot climates, mao kini ang - 5°C hangtod + 50°C. Sa altitudes hangtod 1000 metres, ang preferred minimum ambient temperatures alang sa low - temperature test mao ang - 10°C, - 25°C, - 30°C, ug - 40°C. Sa mga outdoor applications, ang design sa mga vacuum circuit breakers kinahanglan mag-account sa rapid temperature changes. Sa India, daghan nga lugar sa mga rehiyon sama sa Kashmir, Himachal Pradesh, Uttarakhand, ug Sikkim adunay sulod nga temperatura variations.
Ang temperatura mahimong mababa hangtod -25°C. Sa mga lugar kini, ang mga issues related sa cold conditions mas naka-exacerbate tungod sa frequent occurrences sa phenomena sama sa wind chill ug snow blizzards. Sa panahon sa summer, sa daghang bahin sa India, ang temperatura mahimong taas hangtod 50°C. Ang mga manufacturer nga nag-export og circuit breakers sa mga nasod nga adunay extremely low o high temperatures kinahanglan mogamit sa performance sa ilang mga produkto sa kini nga extreme climatic conditions.
Kini nga paper delves sa performance sa 36 kV - class outdoor vacuum circuit breakers (VCBs) sa simulated environmental conditions sumala sa IEC 62271 - 100. Ang mga tests discussed dinhi inklusibo sa (a) ang low - temperature test ug (b) ang high - temperature test. Padulong, ang paper explores ang operating time, ang time difference between poles, ug ang charging time sa operating mechanism sa 36 kV - class outdoor VCB.
Low - Temperature Test
Arangkada mahimong makab-ot sa performance sa mga outdoor VCBs sa low - temperature conditions, ang procedure specified sa IEC - 62271 - 100 gipili isip reference. Kini nga IEC standard stipulates nga para sa single - enclosure circuit breakers uban sa common operating mechanism, ang three - phase tests mahimong gibuhat. Para sa multi - enclosure circuit breakers uban sa independent poles, ang testing sa usa ka complete pole allowed. Sa mga kaso diin may test facility limitations, ang multi - enclosure circuit breakers mahimong gitest gamit ang usa o mas daghan pa sa mga sumala, provided nga ang mechanical operating conditions sa circuit breaker sa test setup dili mas favorable kontra sa normal conditions:
Sa panahon sa test, wala ma allowed ang maintenance, part replacement, o readjustment sa circuit breaker. Unless ang design sa circuit breaker ang nag-require og heat source, ang liquid o gas supplies sa circuit breaker dapat sa test air temperature.
Ang sumala nga operating characteristics sa breaker dapat ig-test:
Closing time
Opening time
Time difference between poles
Time spread between units of one pole (if multi - pole tested)
Recharging time of the operating device
Consumption of the control circuit
Consumption of tripping devices and recording of shunt releases
Duration of closing and opening command impulses
Tightness test if applicable
Gas pressure if applicable
Resistance of the main circuit
Time - travel chart
Kini nga characteristics dapat irecord sa:
Pressure - changed parameters dili applicable sa VCBs tungod kay ang contactor nahimutang sa vacuum bottles ug kini nga vacuum interrupter assembly giecapsulated sa air - insulated porcelain housing para sa outdoor application.
Ang test sequence para sa low - temperature test defined sa cl. 6.101.3.3 sa IEC 62271 - 100. Initial operating characteristics [1.4] characterized human sa pag-expose sa breaker sa 20 ± 5°C. Human sa initial examination sa circuit breaker sa closed position ang temperatura mapadako sa minimum ambient air temperature sumala sa temperature category. Ang breaker mahimong gipakilid sa closed position sa 24 hours uban sa anti - condensation heaters on. Human sa 24 hours ang breaker opened & closed sa rated values of supply voltage. Ang opening ug closing time irecord aron mopuli sa low - temperature operating characteristics. Pagkatapos ang supply sa anti - condensation heaters disconnected sa usa ka period of time (t₁) sumala sa manufacturer, subject sa minimum of two hours. Sa kini nga interval, alarms allowed pero lockouts dili allowed. Human sa time t₁ ang breaker opened ug ang opening time irecord. Kon posible, ang mechanical travel characteristics usab imasu aron mopuli sa interrupting capacity.
Ang breaker mahimong gipakilid sa open position sa 24 hours human ang breaker closed ug opened. Pagkatapos 50 CO operations performed, ang unang tulo CO operations performed without any delay. Balance CO operations performed as C - tₑ - O - tₑ. Time tₑ ang time period between operations. A 3 - minute interval will be allowed for each cycle or sequence. Human sa completion sa 50 CO operations ang temperatura sa climatic test chamber mapadako sa rate of 10 K/hour. Sa transition period, C - tₑ - O - tₑ ug O - tₑ - C - tₑ - O operations performed aron ang breaker remains in closed ug open position sa 30 minutes period between the operating sequences. Human ang circuit breaker stabilizes sa ambient temperature ang repeat measurement sa operating characteristics gibuhat sa 20 ± 5°C para sa comparison sa initial characteristics sa 20 ± 5°C.
CPRI has been conducting low - and high - temperature tests on Medium High Voltage (MHV) switchgear up to 36 kV for over ten years. Figure 1 shows a typical test arrangement for an outdoor 36 kV vacuum circuit breaker (VCB) installed in the test chamber for high - and low - temperature testing.
Experimental results for a 36 kV - class outdoor VCB during low - and high - temperature tests are presented. The VCBs tested were equipped with spring operating mechanisms.
The high - temperature test was performed at +55°C, and the low - temperature tests were performed at -10°C and -25°C. The following characteristics were examined to analyze the performance of the VCB:
Closing and Opening time (Operating Time)：Closing time is defined as the interval of time between energizing the closing circuit, with the circuit breaker in the open position, and the instant when the contacts touch in all poles.Opening time of a circuit breaker is defined as the interval of time between the instant of energizing the opening release, with the circuit breaker in the closed position, and the instant when arcing contacts separate in all poles.
To obtain volumetric data, the average value of the operating times of all three poles is considered for comparison purposes. Since the time spread between poles has been compared, the maximum change between the maximum and minimum time of individual poles is automatically represented.
a) Time Spread between poles
b) Characteristic of the recharging device, such as recharging time and current consumption.
c) Change in operating characteristics in reference to the initial operating characteristics.
The performance of the breakers during high - and low - temperature tests has been compared with reference to the above - mentioned characteristics, and the results are discussed in the subsequent sections.
Performance evaluation at high temperature
The results of the high - temperature test are presented in Table 1. Initial characteristics were measured at 20°C. IEC 62271 - 100 does not specify any value for operating time or closing time. The measured initial opening times are about 36 ms, and the closing time is around 44 ms. Similarly, the recharging time of the operating device ranges from 9.6 sec to 11.3 sec, and the recharging current is in the range of 2.8 A to 3.1 A.
After 24 hours of exposure to 55°C with the breaker in the closed position, the opening time and closing time uniformly increased by about 5%. After a further 24 - hour exposure to 55°C with the breaker in the open position, the closing time increased by about 2.5%, and the opening time increased by 4%.
There was no significant change in the time spread between poles for all three test samples during the entire test. Hence, it can be inferred that the behavior is similar in all the poles of the VCB.The recharging time decreased from 11.3 sec to 9.6 sec, but the current changed from 2.9 A to 3.4 A.
When comparing the opening and closing times between the initial and final values at ambient temperatures, a change of less than 1% in the operating time was observed, which is negligible.
The initial operating characteristics were measured at 20°C. The measured initial values of the opening time were around 36 ms, and the closing time was 44 ms. Similarly, the recharging time of the operating device was 10.6 sec, and the recharging device current was 2.8 A.
After 24 hours of exposure to -10°C with the breaker in the closed position, the opening time decreased by about 0.7%, and the closing time increased by about 2%, with no significant change.
During the two - hour period without anti - condensation heaters, the opening time decreased by 1.36%.After a further 24 hours of exposure to -10°C with the breaker in the open position, the closing time increased by about 3%, and the opening time has decreased by about 2%.
During the final test at ambient temperature, the change was less than 1%. Throughout the entire low - temperature test period at -10°C, there was no significant change in the time spread between poles.
The performance of the breaker at various temperatures, starting from +55°C, -10°C, and -25°C, is presented in Table 1.
Significant changes in operating time were observed when the breaker operated at a low temperature of -25°C. The results in Table 3 indicate that the breaker exhibited sluggishness during opening and closing at -25°C. The percentage change in operating time at -25°C was notably different. After 24 hours of exposure, the opening time increased by 30%, and the closing time increased by approximately 25%. Similarly, after the anti - condensation heating elements were turned off for two hours, the opening time increased by 46%. Further exposure for 24 hours at -25°C with the breaker in the open position and the anti - condensation heating element supply restored led to a 44% increase in the opening time and a 21% increase in the closing time. The timing graphs for closing time and opening time recorded during the test clearly show these changes.
The test at an ambient temperature of 20°C is shown in Figure 2. The timing graphs of the closing time recorded after 50 hours of exposure at -25°C are provided in Figure 3. When compared, the sluggishness of the breaker at -25°C is clearly evident.
When compared with its performance at -10°C, where the change in operating time was only around 0.5% to 3%, the breaker's characteristics at -25°C have deteriorated significantly. At -25°C, the operating - time changes during various stages of the test reached approximately 45%.
This paper presents the experimental results of comparing the performance of 36 kV - class outdoor vacuum circuit breakers (VCBs) during low - and high - temperature tests in accordance with IEC 62271 - 100.
The key findings of this paper are as follows:
During the high - temperature test at 55°C, the outdoor VCBs performed satisfactorily. The observed changes in operating time and time spreads between poles were insignificant.
During the low - temperature test at -10°C, the changes in operating time and time spread between poles were insignificant.
Significant changes in operating time were observed when the breaker operated at a low temperature of -25°C. The observed changes in opening time ranged from 20% to 46%, and changes in closing time were in the range of 25% to 43%.
The tests conducted indicate that even if an outdoor VCB can operate normally at -10°C, there is no guarantee that it will perform the same in colder conditions such as -25°C. Thus, it is essential to verify its performance at the required low temperature.
