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delineation of substation coverage area 1
- Thread starter yeahyeah
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One rule of thumb is that you get about a mile of transmission distance for each 1,000 volts of idstributiojn voltage. However, this rule give too little voltage for short distance and slightly too much for longer distances.
Also, on wye connected distribution ( most of the U.S. ) the voltage drop performance for single phase motors when they are starting on a long distribution circuit will be limited by the phase to neutral voltage when using the typical phase to neutral distribution transformers. There is nothing that says that single phase transformers cannot be connected phase to phase on a wye supply system other than that you need 2 fuses and hot wires instead of 1 fuse and hot wire which is more expensive.
However, different voltages have advantages and disadvantages. The reasons why you see a lot of 4,800 volt delta and 4,800Y8,320 volt distribution on older systems are:
1. It was the highest voltage that could be hot gloved with leather hot line gloves. The invention of molded rubber gloves withbleather protectors raised the limit to 19,920Y43,500 volts.
2. It was the highest voltage that fused protector blocks for open wire telephone lines could interrupt.
3. It was the highest voltage that could be used with unshielded insulated wire. The new upper limit is 7,970Y13,800 volts.
Nowdays the most popular voltage are:
7,200Y12,470 volts
7,620Y13,200 volts
7,970Y13,800 volts all 3 of these voltage produce the most resonable fuse and transformer cost for residential and small commercial loads. These voltages can also be used with automatic reclosing of circuit breakers.
Slightly less popular but growing in popularity are:
14,400Y24,940
19,920Y34,500
13,200Y23,000
22,000Y38,000 volts These higher voltage have some advantages for larger industrial and commercial loads. They are NOT amenable to automatic reclosing of circuit breakers except for low amperage circuits.
Another consideration is that in high lightning areas such as Pittsburgh, PA automatic reclosing does not work because the mountain uplift creates rather intense thuderstorms. The result is lightning clusters that can pound the heck out of a distribution circuit for a say 3 minutes. In this case what you need is manual reclosing by the power dispatcher who also has access to a weather radar signal.
Also, on wye connected distribution ( most of the U.S. ) the voltage drop performance for single phase motors when they are starting on a long distribution circuit will be limited by the phase to neutral voltage when using the typical phase to neutral distribution transformers. There is nothing that says that single phase transformers cannot be connected phase to phase on a wye supply system other than that you need 2 fuses and hot wires instead of 1 fuse and hot wire which is more expensive.
However, different voltages have advantages and disadvantages. The reasons why you see a lot of 4,800 volt delta and 4,800Y8,320 volt distribution on older systems are:
1. It was the highest voltage that could be hot gloved with leather hot line gloves. The invention of molded rubber gloves withbleather protectors raised the limit to 19,920Y43,500 volts.
2. It was the highest voltage that fused protector blocks for open wire telephone lines could interrupt.
3. It was the highest voltage that could be used with unshielded insulated wire. The new upper limit is 7,970Y13,800 volts.
Nowdays the most popular voltage are:
7,200Y12,470 volts
7,620Y13,200 volts
7,970Y13,800 volts all 3 of these voltage produce the most resonable fuse and transformer cost for residential and small commercial loads. These voltages can also be used with automatic reclosing of circuit breakers.
Slightly less popular but growing in popularity are:
14,400Y24,940
19,920Y34,500
13,200Y23,000
22,000Y38,000 volts These higher voltage have some advantages for larger industrial and commercial loads. They are NOT amenable to automatic reclosing of circuit breakers except for low amperage circuits.
Another consideration is that in high lightning areas such as Pittsburgh, PA automatic reclosing does not work because the mountain uplift creates rather intense thuderstorms. The result is lightning clusters that can pound the heck out of a distribution circuit for a say 3 minutes. In this case what you need is manual reclosing by the power dispatcher who also has access to a weather radar signal.
Right before we moved to Pittsburh, PA in 1971 Duquesne Light Company elected to set up all of the circuit breakers and oil section switches on their 14,400Y24,940 distribution using manual reclosing by means of their own telephone system. This was a matter that they could not fight GOD.
Our power supplier was Penn Power and even though they had automatic reclosing of the 4,800Y8,320 lines, the typical summer thunderstorm would exhaust the automatic recloser and they would end up having to do manual reclosing. One problem was that they were still using equipment dating back to when Penn Power was known as the Harmony Shortline Railroad which folded in 1930.
Interstingly, Cleveland Electric Illuminating Company uses manual reclosing on 19,920Y34,500 volts but uses automatic reclosing on 7,620Y13,200, 80,000Y138,000, and 200Y435 KV. The 34,500 subtransmission serves quite a bit of both factories and shopping centers as well as older 4,400 delta distribution. Evidentally waiting a few minutes before reclosing reduces harm to customer equipment particularly commercial refrigeration.
Our power supplier was Penn Power and even though they had automatic reclosing of the 4,800Y8,320 lines, the typical summer thunderstorm would exhaust the automatic recloser and they would end up having to do manual reclosing. One problem was that they were still using equipment dating back to when Penn Power was known as the Harmony Shortline Railroad which folded in 1930.
Interstingly, Cleveland Electric Illuminating Company uses manual reclosing on 19,920Y34,500 volts but uses automatic reclosing on 7,620Y13,200, 80,000Y138,000, and 200Y435 KV. The 34,500 subtransmission serves quite a bit of both factories and shopping centers as well as older 4,400 delta distribution. Evidentally waiting a few minutes before reclosing reduces harm to customer equipment particularly commercial refrigeration.
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