Insulation in a power transmission system
View Patent ↗A substation has a converter comprising a first set (S 1 ) of series connected converter valve elements provided between a first (V 1 ) and a second (V 2 ) potential, where the absolute value of the second potential is higher than the absolute value of the first potential, and a second set (S 2 ) of converter valve elements, comprising at least one converter valve element, provided between the second and a third potential (V 3 ), where the absolute value of the third potential is higher than the absolute value of the second potential and all converter valve elements of the second set are placed inside one or more casings ( 28 ) placed on elongated post-like insulation ( 24 ), where the potential of the end of the post-like insulation on which the casings are placed is in a range between the second and the third potential, while the other end of the post like insulation is at ground potential.
1. A substation of a power transmission system having a converter for conversion between AC and DC, said converter comprising:
a first set of series connected converter valve elements provided together in a phase leg between a first and a second potential, where the absolute value of the second potential is higher than the absolute value of the first potential, and
a second set of converter valve elements provided in the same phase leg between the second and a third potential, where the absolute value of the third potential is higher than the absolute value of the second potential, said second set comprising at least one converter valve element,
wherein
the converter valve elements of the first set of converter valve elements are placed in a common enclosure in the form of a valve hall provided at the first potential,
converter valve elements of the first set are connected to the converter valve elements of the second set via a bushing designed for withstanding voltages having potentials at the second potential,
all converter valve elements of the second set are provided inside one or more casings placed on elongated post-like insulation, where the potential of the end of the post-like insulation on which said casings are placed is in a range between the second potential and the third potential, while the other end of said post-like insulation has ground potential, and
the casing of at least one converter valve element in the second set is connected to the second potential.
2. The substation according to claim 1 , wherein the converter valve element in the second set connected to the third potential is provided with a connection terminal provided through a bushing designed to withstand voltages having a potential that is the difference between the absolute values of the third and second potentials.
3. The substation according to claim 1 , wherein the second set of converter valve elements include at least two converter valve elements, and each casing of the second set of converter valve elements has a potential that is at the mid point between the second and third potential.
4. The substation according to claim 1 , further comprising a set of transformers, wherein there is at least one transformer in the set of transformers connected between converter valve elements in the second set of converter valve elements.
5. The substation according to claim 4 , wherein the transformers connected to the second set of converter valve elements are each placed on elongated post-like insulation, where the potential of the end of the insulation where the transformers are placed in a range between the second potential and the midpoint between the second and third potential.
6. The substation, according to claim 5 , wherein the transformers are placed at the second potential.
7. The substation according to claim 5 , wherein the transformers are placed at a potential that is at the midpoint between the second and third potential.
8. The substation according to claim 2 , wherein the second set of converter valve elements include at least two converter valve elements, and each casing of the second set of converter valve elements has a potential that is at the mid point between the second and third potential.
9. The substation according to claim 2 , further comprising a set of transformers, wherein there is at least one transformer in the set of transformers connected between converter valve elements in the second set of converter valve elements.
10. The substation according to claim 3 , further comprising a set of transformers, wherein there is at least one transformer in the set of transformers connected between converter valve elements in the second set of converter valve elements.