WO2022125255A1

WO2022125255A1 - Phase balancing and lv mesh switching

Info

Publication number: WO2022125255A1
Application number: PCT/US2021/058923
Authority: WO
Inventors: Daniel Desmond; Gregory WILK; Michael G. Ennis; Henry KOWALYSHEN
Original assignee: S&C Electric Company
Priority date: 2020-12-07
Filing date: 2021-11-11
Publication date: 2022-06-16

Abstract

A phase balancer switching device that switches input phases on one side of the device to select output phases on an opposite side of the switch for load balancing purposes in a low voltage power distribution network. The device includes an X-terminal having a first phase X-terminal line, a second phase X-terminal line and a third phase X-terminal line, a Y-terminal having a first phase Y-terminal line, a second phase Y-terminal line and a third phase Y-terminal line, and a switch electrically coupled to the X-terminal and the Y-terminal, where the switch includes a configuration of switch parts that are controlled to selectively connect the first, second and third phase X-terminal lines to the first, second and third phase Y-terminal lines.

Description

PHASE BALANCING AND LV MESH SWITCHING

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority from the United States Provisional Application No. 63/122,148, filed on December 7, 2020, the disclosure of which is hereby expressly incorporated herein by reference for all purposes.

BACKGROUND

Field

[0002] This disclosure relates generally to a phase balancer switch and, more particularly, to a phase balancer switch that switches input phases on one side of the switch to select output phases on an opposite side of the switch for load balancing purposes in a low voltage power distribution network.

Discussion

[0003] An electrical power distribution network, often referred to as an electrical grid, typically includes a number of power generation plants each having a number of power generators, such as gas turbines, nuclear reactors, coal-fired generators, hydro-electric dams, etc. The power plants provide power at a variety of medium voltages that are then stepped up by transformers to a high voltage AC signal to be connected to high voltage transmission lines that deliver electrical power to a number of substations typically located within a community, where the voltage is stepped down to a medium voltage for distribution. The substations provide the medium voltage power to a number of three-phase feeders comprised of three single-phase feeder lines that carry the same current, but are 120° apart in phase. For US-based power distribution networks, a number of single-phase lateral lines are tapped off of the three- phase feeder lines that provide the medium voltage to various distribution transformers, where the voltage is stepped down to a low voltage and is provided to a number of loads, such as homes, businesses, etc.

[0004] Periodically, line to ground faults occur in a distribution network as a result of various things, such as animals touching the lines, lightning strikes, tree branches falling on the lines, vehicle collisions with utility poles, etc. These faults may create a short-circuit that increases the load on the particular line, which may cause the current flow on the line from the substation to significantly increase, for example, several times above the normal current, along the fault path. However, some line to ground faults may only draw a minimal amount of amount. Regardless of the significance of the current draw, the fault must be detected and cleared.

[0005] The substation provides the same current, such as 100 amps, on each of the single-phase feeder lines on the feeder, where the current on the feeder lines is balanced between the lines when no load is connected to the lines. The neutral current, referred to in the industry as the 310 current, relative to the feeder lines is determined by summing the phasor currents on the feeder lines, which would be zero if the current on the lines is balanced. If the lines are balanced, an increase in the calculated neutral current would indicate a line to ground fault that is easily detected even if the increase in current on one of the feeder lines as a result of the fault is minimal. However, because the various lateral lines service a different number and type of loads, the current draw of the loads will not allow perfect load balancing between the lines. Therefore, the magnitude of current load imbalance on the single-phase feeder lines generally determines the ability to detect faults below a certain current level, which has obvious safety concerns. In order to overcome this load balancing problem, utilities will typically monitor in some manner the amount of current being drawn from the single-phase feeder lines at various locations and at various times of day. [0006] Power distribution networks are moving towards providing the ability to have power flow in both directions from different power sources, such as battery sources, solar cells, wind farms, etc., using normally open switches. Further, with the increase in electrical vehicles and other similar types of electrical systems, the load on the network can fluctuate causing unpredictable electrical behavior. Thus, certain electrical activity, such as charging an electric vehicle, that needs to be predictable and stable may be affected by such fluctuations. For example, one of the drawbacks of electric vehicle charging is that electric vehicles are connected single-phase, and typically are charged overnight during a low-use window, i.e. , 2-6 AM, or charged during high load periods, such as 6PM when a user returns home from work. These single-phase loads are significant and unusual for the network, especially low voltage (LV) grids in certain places like the UK.

[0007] Most residential and many commercial loads are fed by a single-phase, for example, tapped off of a three-phase LV feeder. Imbalance in current magnitude between the phases can occur if customers wired to one phase draw significantly greater current than customers connected to the other phases. These imbalances in current can cause voltage imbalance along the LV distribution line, and increased power losses at the unbalanced substation transformer. Additionally, LV DG throughout the LV distribution network can cause voltage fluctuations and also redirect power flows in unpredictable and unexpected directions. Other causes of these phase imbalances include increases in electrical vehicle charging, bad electrical contacts, system faults, unsuitable shunt capacitor banks installations, electrification of residential heating, temporary usage of large loads, such as a single-phase motor, home battery installations, etc.

SUMMARY [0008] The present disclosure describes a phase balancer switching device that switches input phases on one side of the device to select output phases on an opposite side of the device for load balancing purposes in a low voltage power distribution network. The device includes an X-terminal having a first phase X-terminal line, a second phase X-terminal line and a third phase X- terminal line, a Y-terminal having a first phase Y-terminal line, a second phase Y- terminal line and a third phase Y-terminal line, and a switch electrically coupled to the X-terminal and the Y-terminal, where the switch includes a configuration of switch parts that are controlled to selectively connect the first, second and third phase X-terminal lines to the first, second and third phase Y-terminal lines.

[0009] Additional features of the present disclosure will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a schematic diagram of a low voltage power distribution network including linkboxes dispersed between power sources;

[0010] Figure 2 is an illustration of a phase balancer switching device that can be employed in the linkboxes in the network;

[0011] Figure 3 is a partial top view of a phase balancer switch that can be used in the phase balancer switching device shown in figure 2;

[0012] Figure 4 is a partial isometric view of the phase balancer switch shown in figure 3;

[0013] Figure 5 is an another partial isometric view of the phase balancer switch shown in figure 3;

[0014] Figure 6 is an isometric view of another phase balancer switch that can be used in the phase balancer switching device shown in figure 2;

[0015] Figure 7 is a front view of the phase balancer switch shown in figure 6; [0016] Figure 8 is a top view of the phase balancer switch shown in figure 6; and

[0017] Figure 9 is a top view of another phase balancer switch that can be used in the phase balancer switching device shown in figure 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The following discussion of the embodiments of the disclosure directed to a phase balancer switch that switches input phases on one side of the switch to select output phases on an opposite side of the switch for load balancing purposes in a power distribution network is merely exemplary in nature, and is in no way intended to limit the disclosure or its applications or uses.

[0019] This disclosure proposes a phase balancer switch that can reconfigure the phase connections in a low voltage network to alleviate imbalance for specific lateral lines or neighborhoods so as to reduce system power losses and allow for better utilization of MV equipment. An autonomous operation of the switch through internal mechanisms and/or actuators simplifies efforts for the distribution system operator/distribution network operator (DSO/DNO). Additionally, the autonomous operation of the switch decreases exposure to energized components for field workers by eliminating manual install or uninstall links in the link boxes. The switch can also provide monitoring on a portion of the network where the DNO/DSO previously did not have insight, but is somewhat dependent on the type of communications infrastructure made available by the DNO/DSO. Further, in concert with the substation fuses or recloser, the switch could provide automatic fault isolation.

[0020] The various phase balancer switches described in this disclosure provide one technique for addressing the problems described above by balancing the current flow across phases, and/or adjusting the total power output from a particular substation transformer. The general concept is a three- phase, two-terminal low voltage (LV) switch that can map the input phases A, B and C to any combination of output phases A, B and C, such as BCA, CAB and ABC, including restricted operation where the Y-terminal holds the same phase rotation as the X-terminal. The concept also includes a series isolating switch to allow for movement of a normally-open point, as well as to allow for isolation during switching operations. The phase balancer switch can be retrofittable into existing underground linkboxes.

[0021] Figure 1 is a schematic type diagram of a low voltage power distribution network 10 including a pair of power sources 12 and 14, such as electrical ring-main-unit (RMU) substations, that place low voltage power on a number of, here four, three-phase LV feeders 16. Each power source 12 and 14 includes disconnect switches 18, a fault interrupting switch 20, an MV:LV transformer 22 and a plurality of fuses 24, one for each feeder 16, provided in an LV feeder panel 26. The LV feeders 16 typically run underground through residential areas, where relevant junctions (typically splices), tap directly off of the cabling to consumers. Linkboxes 28 are dispersed throughout the network 10, and are junction points between the power sources 12 and 14 as well as accessible disconnect points for utility crews.

[0022] Figure 2 is an illustration of a phase balancer switching device 58 of the type referred to above that can be used in the linkboxes 28 for the purposes discussed herein. The phase balancer switching device 58 connects A, B and C phases on lines 30, 32 and 34, respectively, at an X- terminal 36 of the device 58 to any possible combination of A, B and C phases on lines 38, 40 and 42, respectively, at a Y-terminal 44 of the device 58. The mapping of the X-terminal phases to the Y-terminal phases is provided by a series isolating switches 46, for example, three single-phase switching devices or one ganged three-phase switching device, that switches the lines 30, 32 and 24 to the lines 38, 40 and 42 when current flow is from left to right and switches the lines 38, 40 and 42 to the lines 30, 32 and 34 when current flow is from right to left. Voltage sensors 48 are provided at both the X and Y terminals 42 and 44, and a current sensor 50 is provided internal to the device 58. The device 58 can include a communications device 52 for communicating through a variety of protocols, but communications are not required for operation of the device 58. The decision of when to switch and how to switch the switch 46 is provided by a state machine or control algorithm in a controller 54 that makes use of the measurements from the voltage and current sensors 48 and 50, knowledge of the system topology (true radial, radial with normally-open points, or fully meshed), and other configuration parameters. The phase balancer switching device 58 must be able to carry full short-circuit current, but is not required to break it.

[0023] Figure 3 is a partial top view, figure 4 is a partial isometric view and figure 5 is another partial isometric view of a phase balancer switch 60 that can be used as the combination of the switches 46 in the phase balancer switching device 12. The switch 60 includes a contact assembly 62 having an outer stationary contact support ring 64 and a rotatable central column 66 concentric with the ring 64 and defining a gap 68 therebetween. A first conductor rod 70 is connected to the line 38 at the Y-terminal 44, a second conductor rod 72 is connected to the line 40 at the Y-terminal 44, and a third conductor rod 74 is connected to the line 42 at the Y-terminal 44 that extend into the gap 68 and are rigidly attached at 120° apart to an outer surface 76 of the column 66. A series of nine perimeter contacts 80, 82, 84, 86, 88, 90, 92, 94 and 96 are rigidly attached to an inside surface 100 of the ring 64, extend into the gap 68 and are spaced equidistance apart. A three-leg A-phase map conductor 110 is connected to the contacts 80, 88 and 96 and includes a tab 112 extending from one of the legs that is electrically coupled to the A-phase line 30. A three-leg B-phase map conductor 114 is connected to the contacts 82, 86 and 90 and includes a tab 116 extending from one of the legs that is electrically coupled to the B-phase line 32. A C-phase map conductor 118 is connected to the contacts 84, 92 and 94 and includes a tab 120 extending from one of the legs that is electrically coupled to the C-phase line 34.

[0024] The central column 66 is rotated in 40° increments to move the conductors 110, 114 and 118 from one set of stationary perimeter contacts 80-96 to another set of perimeter contacts 80-96. The conductors 110, 114 and 118 are stacked on top of each other with sufficient clearance, or with a dielectric material placed between them, for worst-case voltage withstand in the network 10. The perimeter contacts 80-96 also have sufficient air/dielectric clearance for worst-case voltage withstand in the network 10.

[0025] The switch 60 also includes a rotation assembly 130 having a shaft 132 that is connected to a gear 134 at one end opposite to the connector assembly 62 and the column 66 at the other end. Gear teeth 136 on the gear 134 engage a gear/motor assembly 138 that rotates the shaft 132, and thus rotates the column 66 in the clockwise direction. The shaft 132 extends through a lower plate 140 having outer teeth 142 that engage a pawl 144, where the position of the teeth 142 aligns with the contacts 80-96. The shaft 132 also extends through an upper plate 148 having outer teeth 150 that engage a pawl 152, where the position of the teeth 150 also aligns with the contacts 80-96. A clock spring 154 between the upper plate 148 and the assembly 62 controls the speed of rotation of the column 66, and winds and puts torque on the plate 148. An unlatching lever 156 is connected by a one way bearing (not shown) to the shaft “kicks” the pawl 152 away from the plate 148 to move the plate 148 40° to the next tooth 150. An identical ratchet and pawl system (not shown) is connected in an opposite rotational orientation underneath the clock spring 154 so that a counterclockwise motor rotation can rotate the center column 66. It is noted that other actuation systems, such as spring mechanisms, electromagnetic actuators, piezoelectric actuators, etc., can be employed to rotate the central column 66.

[0026] Figure 6 is an isometric view, figure 7 is a front view and figure 8 is a top view of a phase balancer switch 170 that can also be used as the combination of the switches 46 in the phase balancer switching device 12. The switch 170 includes a U-shaped support structure 172 having opposing side walls 174 and 176 attached to a base plate 178. The switch 170 also includes a rotatable A-phase rod 180 extending between the walls 174 and 176 and including an X-terminal connection tab 182 extending from the wall 174 opposite to the wall 176 to be electrically coupled to the line 30, a rotatable B-phase rod 184 extending between the walls 174 and 176 and including an X-terminal connection tab 186 extending from the wall 174 opposite to the wall 176 to be electrically coupled to the line 32, and a rotatable C-phase rod 188 extending between the walls 174 and 176 and including an X-terminal connection tab 190 extending from the wall 174 opposite to the wall 176 to be electrically coupled to the line 34. A motor 200 mounted to the base plate 178 rotates the rod 180, a motor 202 mounted to the base plate 178 rotates the rod 184, and a motor 204 mounted to the base plate 178 rotates the rod 188. Each rod 180, 184 and 188 includes three contacts 210, 212 and 214 spaced apart along the rods 180, 184 and 188 and positioned 120° apart around the 180, 184 and 188 relative to each other.

[0027] A Y-terminal A-phase conductor 220 is secured to the base plate 178 to be electrically coupled to the line 38 at tab 222, a Y-terminal B- phase conductor 224 is secured to the base plate 178 to be electrically coupled to the line 40 at tab 226, and a Y-terminal C-phase conductor 228 is secured to the base plate 178 to be electrically coupled to the line 42 at tab 230, where the conductors 220, 224 and 228 are parallel and spaced apart the same distance as the contacts 210, 212 and 214. A series of three contacts 232, 234 and 236 are electrically coupled to each of the conductors 220, 224 and 228 and spaced apart the distance between the rods 180, 184 and 188. At any point in time, one of the contacts 210, 212 and 214 on each rod 180, 184 and 188 is electrically coupled to one of the three contacts 232, 234 and 236. The motors 200, 202 and 204 selectively rotate the rods 180, 184 and 188 to control which of the tabs 210, 212 and 214 on a particular rod 180, 184 and 188 is connected to a particular one of the contacts 232, 234 and 236 so as to selectively control which X- terminal line 30, 32 and 34 is connected to which Y-terminal line 38, 40 and 42. This switching is coordinated by a control that prevents phase-to-phase shorts, or possibly utilizes a mechanical lock (not shown) that prevents phase-to-phase shorts.

[0028] In another embodiment, the switch 170 could be operated by solely by one actuation method (motor or otherwise) that simultaneously operates all three rotating rods 180, 184 and 188 to change from one configuration to the next. Depending on the mating system from the actuator to the contacts 232, 234 and 236, this switch may only be able to achieve a subset of all possible phase rotations. Note that bidirectional actuation is required to achieve state transition between any of the modes in one operation. If the actuation is unidirectional, moving from one mode to another may take upwards of six rotations. For example, mode 1 to mode 5 requires two 120° rotations on each rod to achieve the new mode.

[0029] Figure 9 is a top view of another phase balancer switch 250 that can be used as the combination of the phase balancer switches 46 in the device 58. The switch 250 includes an outer translating cylinder 252 and an inner rotational cylinder 254 concentric therewith and defining a gap 256 therebetween. A series of three contacts 258, 260 and 262 are formed to an inside surface 264 of the cylinder 252 and extend into the gap 256, where each contact 258, 260 and 262 is electrically coupled to one of the lines 30, 32 and 34, and a series of three contacts 266, 268 and 270 are formed to an outside surface 272 of the cylinder 254 and extend into the gap 256, where each contact 266, 268 and 270 is electrically coupled to one of the lines 38, 40 and 42. The inner cylinder 254 rotates one position clockwise or one position counter-clockwise from its starting position, and the outer cylinder 252 translates one position forward (into or out of the page) from its starting position so that the contacts 258, 260 and 262 connects to the contacts 266, 268 and 270 of the inner cylinder 254. Note that in the translated state, two of the contacts are transposed.

[0030] The foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the disclosure as defined in the following claims.

Claims

CLAIMS What is Claimed is:

1 . A phase balancer switching device comprising: an X-terminal including a first phase X-terminal line, a second phase X-terminal line and a third phase X-terminal line; a Y-terminal including a first phase Y-terminal line, a second phase Y-terminal line and a third phase Y-terminal line; and a switch being electrically coupled to the X-terminal and the Y- terminal, the switch including a configuration of switch parts that are controlled to selectively connect the first, second and third phase X-terminal lines to the first, second and third phase Y-terminal lines.

2. The device according to claim 1 wherein the switch parts include an outer stationary ring, an inner rotatable column concentric with and internal to the ring and defining a gap therebetween, three conductor bars secured to an outer surface of the column 120° apart from each other and each being electrically coupled to one of the first, second or third phase Y-terminal lines, a plurality of perimeter contacts secured to an inner surface of the ring and being equally spaced apart and extending into the gap, a first three-leg map conductor electrically coupled to the first phase X-terminal phase line and a first set of three of the perimeter contacts, a second three-leg map conductor electrically coupled to the second phase X-terminal phase line and a second set of three of the perimeter contacts, and a third three-leg map conductor electrically coupled to the third phase X-terminal phase line and a third set of three of the perimeter contacts, wherein the column is rotated to selectively couple the conductor bars to select ones of the perimeter contacts.

3. The device according to claim 2 wherein the switch parts further include a gear and pawl assembly to control the rotation of the column in predetermined increments.

4. The device according to claim 3 wherein the column rotates in both a clockwise and counter-clockwise direction.

5. The device according to claim 4 wherein the column is rotated +40° and -40°.

6. The device according to claim 1 wherein the switch parts include a first rotatable rod electrically coupled to the first phase X-terminal line at one end and a first motor at an opposite end, a second rotatable rod electrically coupled to the second phase X-terminal line at one end and a second motor at an opposite end, and a third rotatable rod electrically coupled to the third phase X- terminal line at one end and a third motor at an opposite end, each rod including three rod contacts that are spaced apart along the rod and 120° apart around the rod.

7. The device according to claim 6 wherein the switch parts further include a first Y-terminal phase conductor electrically coupled to the first phase Y-terminal line, a second Y-terminal phase conductor electrically coupled to the second phase Y-terminal line, and a third Y-terminal phase conductor electrically coupled to the third phase Y-terminal line, each phase conductor being aligned with one of the rod contacts on each rod.

8. The device according to claim 7 wherein the switch parts further include nine phase contacts where three of the phase contacts are electrically coupled to each phase conductor and being spaced apart so that each phase contact aligns with one of the rod contacts on one of the rods, and wherein each of the rod contacts is electrically coupled to one of the phase contacts to as to electrically coupled one of the X-terminal lines to one of the Y-terminal lines and rotation of the rods by the motors causes the rod contacts to be electrically coupled to a different one of the phase contacts so as to electrically couple the X- terminal lines to a different one of the Y-terminal lines.

9. The device according to claim 1 wherein the switch parts include an outer translating ring, an inner rotatable column concentric with and internal to the ring and defining a gap therebetween, three conductor bars secured to an outer surface of the column 120° apart from each other and each being electrically coupled to one of the first, second or third phase Y-terminal lines, and six perimeter contacts secured to an inner surface of the ring and being equally spaced apart and extending into the gap.

10. The device according to claim 1 further comprising voltage and current sensors for measuring the voltage and current on the first, second and third phase X-terminal lines and the first, second and third phase Y-terminal lines.

11. The device according to claim 1 further comprising a controller for controlling the connection between the first, second and third phase X-terminal lines and the first, second and third phase Y-terminal lines.

12. The device according to claim 1 wherein the device is part of a linkbox provided between power sources in a low voltage power distribution network.

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13. The device according to claim 1 further comprising a communications device that allows the device to communicate with other components in the network.

14. A phase balancer switching device for a low voltage power distribution network, the device comprising: an X-terminal including a first phase X-terminal line, a second phase X-terminal line and a third phase X-terminal line; a Y-terminal including a first phase Y-terminal line, a second phase Y-terminal line and a third phase Y-terminal line; and a switch being electrically coupled to the X-terminal and the Y- terminal, the switch including an outer stationary ring, an inner rotatable column concentric with and internal to the ring and defining a gap therebetween, three conductor bars secured to an outer surface of the column 120° apart from each other and each being electrically coupled to one of the first, second or third phase Y-terminal lines, a plurality of perimeter contacts secured to an inner surface of the ring and being equally spaced apart and extending into the gap, a first three-leg map conductor electrically coupled to the first phase X-terminal phase line and a first set of three of the perimeter contacts, a second three-leg map conductor electrically coupled to the second phase X-terminal phase line and a second set of three of the perimeter contacts, and a third three-leg map conductor electrically coupled to the third phase X-terminal phase line and a third set of three of the perimeter contacts, wherein the column is rotated to selectively couple the conductor bars to select ones of the perimeter contacts.

15. The device according to claim 14 wherein the switch parts further include a gear and pawl assembly to control the rotation of the column in predetermined increments.

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16. The device according to claim 15 wherein the column rotates in both a clockwise and counter-clockwise direction +40° and -40°.

17. The device according to claim 14 wherein the device is part of a linkbox provided between power sources in a low voltage power distribution network.

18. A phase balancer switching device for a low voltage power distribution network, the device comprising: an X-terminal including a first phase X-terminal line, a second phase X-terminal line and a third phase X-terminal line; a Y-terminal including a first phase Y-terminal line, a second phase Y-terminal line and a third phase Y-terminal line; and a switch being electrically coupled to the X-terminal and the Y- terminal, the switch including a first rotatable rod electrically coupled to the first phase X-terminal line at one end and a first motor at an opposite end, a second rotatable rod electrically coupled to the second phase X-terminal line at one end and a second motor at an opposite end, and a third rotatable rod electrically coupled to the third phase X-terminal line at one end and a third motor at an opposite end, each rod including three rod contacts that are spaced apart along the rod and 120° apart around the rod, the switch parts further including a first Y- terminal phase conductor electrically coupled to the first phase Y-terminal line, a second Y-terminal phase conductor electrically coupled to the second phase Y- terminal line, and a third Y-terminal phase conductor electrically coupled to the third phase Y-terminal line, each phase conductor being aligned with one of the rod contacts on each rod, the switch parts further including nine phase contacts where three of the phase contacts are electrically coupled to each phase conductor and being spaced apart so that each phase contact aligns with one of the rod contacts on one of the rods, and wherein each of the rod contacts is

16 electrically coupled to one of the phase contacts to as to electrically coupled one of the X-terminal lines to one of the Y-terminal lines and rotation of the rods by the motors causes the rod contacts to be electrically coupled to a different one of the phase contacts so as to electrically couple the X-terminal lines to a different one of the Y-terminal lines.

19. The device according to claim 18 wherein the device is part of a linkbox provided between power sources in a low voltage power distribution network.

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