In many operating environments, it is critical that electronic equipment or other electrically-powered appliances not suffer from interruptions of electrical power. For example, power failure for medical appliances in hospitals can be devastating. Likewise, computer servers in a data center may be performing critical functions related to any of numerous vital (and other) services such as air traffic control, telephone switching, cell towers, and police emergency services, to name but a few; and so providing reliable continuous power for such data centers has long been a major objective. Some appliances can tolerate brief power interruptions but many others cannot, and various methods have been employed to seek to provide uninterrupted electrical power to these critical devices.
Electrical power failures can result from many causes. Some occur from accidents or equipment malfunctions in commercially-provided power. Others may be locally-caused, for example from some kind of malfunction or short circuit within a hospital or a server farm or even in a single rack of computer equipment.
One way of maintaining power to critical appliances, at least on a short-term basis, is to provide a battery backup. Local generators, for example powered by natural gas, are another option. When transferring an electrical load from one power source to another, however, service continuity without any interruption may be critical or, in any event, desired for a number of reasons. Service continuity can be particularly important in the context of loads such as “always on” facilities. To maintain service continuity to such equipment, the power supply chain can be provided with various types of redundancy.
Although service continuity may be important and even paramount, fault isolation has long been equally important in many applications. For example, it can be desirable and even essential to isolate (i) critical loads from any effects of a fault found somewhere in the power delivery supply chain and (i) to isolate a power supply system or parts of a power supply system from effects of a fault occurring in equipment downstream of the power supply.
Various kinds of power supplies and methods of managing electrical power have been devised to seek to meet the requirements of service continuity and fault isolation. They have done so with varying degrees of success, usually at significant cost. To the applicant's knowledge, these prior art systems have not provided sufficient service continuity to critical electrical and electronic appliances while also enabling faults to be safely isolated for maintenance and repair.
The applicant believes that he has, among other things, discovered at least some of the issues, and their severity, recited in the Background above.
One aspect of the present specification provides an electrical power system with service continuity and isolation of faults from active power circuits. In some embodiments, the system includes two source breakers, and two load breakers, each load breaker in series connection with one of the source breakers. Each load breaker has a shunt trip and the source breaker has a lockout relay in controlling communication with the shunt trip. The first source breaker is in a power-receiving connection with a first power source and the second source breaker is in power-receiving connection with a second power source. A controller is in communication with the source breakers to close the first source breaker and open the second source breaker if power is available from the first power source and if the first source breaker is not in a tripped state. If power ceases to be available from the first power source or if the first source breaker trips, the second source breaker is closed and the first source breaker is opened if power is available from the second power source and if the second source breaker is not in a tripped state.
In some examples both source breakers are in power-providing communication with one load through the load breakers. In these examples, the load can be powered from either power source.
In some examples the controller comprises a single unit that communicates with both source breakers, and in other examples the controller comprises two control units, one in controlling communication with each of the source breakers. Using two control units is one way to provide redundancy such that if one controller fails, power can still be provided to the load.
Certain systems include a synchronizer that detects when the two power sources are in sync with each other and communicates this information to the controller. For example, if the power sources provide alternating current (AC), the synchronizer can report when the two power sources are in phase with each other such that one power source can be connected to the load at the same instant as the other is disconnected, providing continuous power to the load through the switching process without stressing either power source.
Some embodiments include more source breakers in power-receiving connection with additional power sources, more load breakers receiving power from the source breakers, and more loads. These embodiments can implement Zipper LogicSM functionality, by which several loads can be switched sequentially among power supplies if one supply fails. For example, there may be a third source breaker similar to the first and in power-receiving connection with the second power source, and a fourth source breaker similar to the first and in power-receiving connection with a third power source. These two source breakers are in power-providing connection through load breakers with a second load. Similarly, a fifth similar to the first and in power-receiving connection with the third power source, and a sixth similar to the first and in power-receiving connection with a fourth power source, may be provided. The fifth and sixth source breakers are in power-providing connection with a third load through additional load breakers.
If power ceases to be available from any of the four power sources, or if any source breaker trips, the controller is in communication with the source breakers to cause the source breakers to establish electrical power connections between the remaining power sources and loads in sequence such that no load is connected to more than one source. Some examples include additional pairs of source breakers and power sources, and so long as the number of power sources exceeds the number of loads, the loads can be sequentially switched among the power sources.
Some embodiments also include an auxiliary breaker in power-carrying connection with an auxiliary power source, for example a generator, a load-bank breaker in power-carrying connection with a load bank bus, a tie breaker in power-receiving connection with the auxiliary and load-bank breakers and in power-providing connection with the source breaker, and a utility breaker in series between the source breaker and the power source. In this embodiment the controller is in communication with the breakers to close the utility breaker if power is available from the power source to which the source breaker is connected, and if not, to close the auxiliary and tie breakers, and if power is not available from the auxiliary power source but is available from the load bank bus, to close the tie and load-bank breakers.
It may happen that two loads lose power from their respective sources but a third auxiliary power source is not being used. In this case, the controller can open the tie breaker and close the auxiliary and load-bank breakers associated with the third auxiliary power source, and close the tie and load-bank breakers for one of the two affected loads. This can enable power to be provided from the third auxiliary power source to the load through the load bank bus even if the third auxiliary power source and the loads are in different subsystems.
An example of a method of managing electrical power in a power distribution system having more power sources than loads includes applying power from a first power source through a first source protector to a load through a first load protector, upon failure of the first power source to provide power or upon trip of the first source protector, applying power from a second power source through a second source protector to the load through a second load protector, and upon trip of the first source protector, locking the first source protector and the first load protector in an open-circuit state. In some examples the load is shut down if the second source protector is tripped.
In another example, if the second power source is already providing power to another load, the loads are redistributed by sequentially switching each load from one power source to another such that all loads are being provided with power and no power source is providing power to more than one load.
In another example, each power source comprises primary and auxiliary power supplies, and failure of a power source to provide power means failure to provide power from its primary and auxiliary power supplies.
In some systems, upon failure of a second load to receive power from its associated power sources, an unused auxiliary power supply is identified and power from the identified auxiliary power supply is applied to the second load. For example, this may be done by connecting the identified auxiliary power supply to a load bank bus.
There are other novel features and aspects of the present specification. They will become apparent as the specification proceeds. In this regard, it is understood that the scope of the invention is to be determined by the claims as issued and not by whether they address any issues set forth in the Background or provide a feature recited in this Brief Summary of Some Aspects of the Specification.
The applicant's preferred and other embodiments are disclosed in the accompanying Figures in which:
Illustrative examples and details are used in the drawings and in this description, but other configurations may exist and may suggest themselves. Parameters such as voltage, temperature, dimensions, and component values are approximate. Terms of orientation such as up, down, top, and bottom are used only for convenience to indicate spatial relationships of components with respect to each other; except as otherwise indicated, orientation with respect to external axes is not critical. For clarity, some known methods and structures have not been described in detail. Methods defined by the claims may comprise steps in addition to those listed, and except as indicated in the claims themselves the steps may be performed in another order than that given. Accordingly, the only limitations are imposed by the claims, not by the drawings or this description.
Some embodiments of the systems and methods described herein may be implemented in various forms of hardware, software, firmware, special purpose processors, or a combination thereof. At least a portion thereof may be implemented as an application comprising program instructions that are tangibly embodied on one or more program storage devices such as hard disks, magnetic floppy disks, RAM, ROM, and CDROM, and executable by any device or machine comprising suitable architecture. Some or all of the instructions may be remotely stored and accessed through a communication facility; for example, execution of remotely-accessed instructions may be referred to as cloud computing. Some of the constituent system components and process steps may be implemented in software, and therefore the connections between system modules or the logic flow of method steps may differ depending on the manner in which they are programmed.
The power input 106 need not take any particular form. In the example of
The first source breaker 102 may be located remotely from the first load breaker 108 and may provide power to it through any convenient power transmission medium. In this example power is carried by one or more conductors through a raceway 130. The lockout relay 104 sends a trip signal to the shunt trip 110 through any suitable means, which in this example is another conductor in the raceway 130. Similarly, power and communication conductors from the second source breaker 114 and lockout relay 116 to the second load breaker 120 and shunt trip 122 are carried through a raceway 132. In other examples the lockout relays may communicate with the shunt trips through differently-located conductors or through a data communication system or wirelessly.
In some examples the first source breaker 102 and lockout relay 104 are installed in a first switchboard 100. Similarly, the second source breaker 114 and lockout relay 116 may be installed in a second switchboard 112. The physical locations of source breakers and load breakers in one or more switchboards can be arranged as convenient and is not critical to the functioning of the components and circuits described herein.
In this example a single controller 124 communicates with both source breakers. In other examples the controller may include more than one control unit each in communication with one source breaker. The control units may be physically installed in or adjacent any switchboards or remotely located as may be convenient. The controller may be programmed or otherwise configured to close the first source breaker 102 and open the second source breaker 114 if power is available at the first power input 106 and if the first source breaker 102 is not in a tripped state, and if power ceases to be available at the first power input 106 or if the first source breaker 102 trips, to close the second source breaker 114 and open the first source breaker 102 if power is available at the second power input 118 and if the second source breaker 114 is not in a tripped state.
In some examples the controller 124 also monitors the load breakers 108 and 120, does not close the first source breaker 102 if the first load breaker 108 is tripped, and does not close the second source breaker 114 if the second load breaker 120 is tripped.
The two load breakers 108 and 120 may feed a power output 134. As with the power inputs 106 and 118, the power output 134 may be just a connection point or a conductor, or it may be a receptacle or some other kind of power connector. The power output may be connected to a load 136. The load 136 may be a computer server, a medical appliance, an air conditioner, a chiller, or most any other kind of electrically-powered device.
In some examples a power synchronizer 134 is in communication with the controller 124 to detect when the power sources 126 and 128 are in sync with each other. For example, the synchronizer might detect when both power supplies have the same direct current (DC) output voltage or when they both have the same frequency or phase angle (or both) in the case of alternating current (AC) power.
The functioning of the various components will now be explained in more detail with reference to
The control 144 can electrically operate the source isolation breakers 140 and 142 so as to feed the load 148 from either of the two power sources 146 and 150. In some embodiments these power sources can be operated as primary and secondary sources or normal and emergency sources. However, for purposes of this description, the power sources are simply referred to as first and second power sources or as Source 1 and Source 2. The control 144 can monitor the status of the breaker transfer pair and of both power sources for acceptability to serve the load. For robustness, the control 144 can include an interlock circuit or mechanism to prevent both of the source isolation breakers from being closed at the same time. In some examples the control 144 includes or is part of a programmable logic controller (PLC).
As an example of operation of the circuit of
By way of example, the control 144 can perform this sequence of operations:
The control 144 can perform the reverse of the above sequence of operations if it subsequently determines that the power provided by the second power source 150 is unacceptable, but the power provided by the first power source 146 is acceptable. More specifically, the control 144 can perform the following sequence of operations:
1. Open the second source isolation breaker 142.
2. Optionally, wait for a period of time before performing other operations.
3. Close the first source isolation breaker 140.
The circuit can in some cases include additional components, or the control 144 can perform other operations or include other circuitry.
As an example of the operation of the circuit of
If the first power source 146 is once again brought online or made available, and the control 144 subsequently determines that the power available from both sources is acceptable, the control 144 may perform the following sequence of operations to transfer the load 148 back to the first power source 146:
The circuit described with reference to
One advantage offered by the circuit of
The circuit of
The load isolation breakers 154 and 156 may be manually operated, normally-closed circuit breakers. Optionally, the circuit can include logic or a hard wired interlock, for example a combination of control wires or circuitry or both, associated with one or more of the breakers 140, 142, 154, and 156 and the control 144 to auto-open one of the source isolation breakers 140 or 142 if the respective downstream load isolation breaker 154 or 156 is opened for any reason, either manually or by protective trip.
The control 144 can electrically operate the first and second source isolation breakers 140 and 142 while the first and second load isolation breakers 154 and 156 are closed, feeding the load 148 from either of the two power sources. The control 144 can monitor the status of the breakers and the power sources to be sure they can serve the load 148. With both load isolation breakers 154 and 156 closed, the operation of the circuit is similar to that already described with reference to
The circuit of
The source isolation breakers 140 and 142 may be electrically operated, either automatically by the control 144 or semi-automatically in response to an input received via a human-machine interface (HMI) such as a touch screen or keypad. The source isolation breakers 140 and 142 can also be operated in response to input received from a remote computer connected to the control 144 by a cable, bus, or network. The load isolation breakers 154 and 156 can be manually operated by pushing a mechanical push button or throwing a lever arm, or electrically-opened by shunt trip as described above.
By means of either one of the control systems 158 and 160 electrically operating the first and second source isolation breakers 140 and 142 while the first and second load isolation breakers 154 and 156 are closed, the load 148 can be fed from either of the two power sources 146 and 150. For example, the first control system 158 can monitor the status of the breakers 140 and 142 and both power sources for acceptability to serve the load. In some cases the first control system 158 can monitor the second source isolation breaker 142 and the second power source 150 directly. In other cases, the first control 158 can receive signals or information regarding the operation of the second source isolation breaker 142 and the second power source 150 from the second control 160. Failure to receive information from the second control system 160 can be interpreted by the first control 158 as a failure of one or both of the second source isolation breaker 142 and the second power source 150. The second control system 160 can be operated in a similar manner. In some examples either or both of the controls 158 and 160 include or are part of one or more PLCs.
But for the option to use either the first control 158 or the second control 160 to operate the first and second source isolation breakers 140 and 142, the circuit of
A potential problem can arise if an electrical fault occurs between the source and load isolation breakers 140 and 154 or between the breakers 142 and 156, especially if the source and load isolation breakers are separated from each other by a distance, installed in separate equipment enclosures. For example, when the first source isolation breaker 140 is closed and the second source isolation breaker 142 is open, and with both of the load isolation breakers 154 and 156 closed, the first source isolation breaker 140 can automatically trip upon the occurrence of a fault between the first source isolation breaker 140 and the first load isolation breaker 154. This trip can be referred to as a protective trip. If a protective trip occurs, an optional lockout relay 162 associated with the first source isolation breaker 140 can be actuated. When actuated, the lockout relay 162 prevents any change from the first source 146 to the second source 150 either manually or automatically by the control 158 or the control 160. As a result, the lockout relay 162 not only prevents the associated source isolation breaker 140 from being reclosed, but also prevents the second source isolation breaker 142 from closing. This interlock prevents the second source isolation breaker 142 from closing on a known fault but at the cost of de-energizing the load. An optional lockout relay 164 associated with the second source isolation breaker 142 operates in a similar manner.
The de-energizing of the load that can result from the use of lockout relays as described above with reference to
By way of example, the circuit of
The lockout relay 116, which is associated with the second source isolation breaker 114, and the shunt trip 122, which is associated with the second load isolation breaker 120, can be used similarly. In this manner, this circuit can provide both fault isolation and service continuity.
The electrically-operated source isolation breakers and manually-operated load isolation breakers shown in
The example of
In some examples, individual switchboards such as 203 and 206, 207 and 210, 211 and 214, or 215 and 218, as shown in
A control 242 is shown as communicating with all the breakers. A single control is shown, but the control 242 may actually comprise a plurality of controls. For example, each breaker unit may have its own control or, as shown in
In this example the power input 202 is in power-receiving communication with a first power source 243. The power inputs 205 and 208 are in power-receiving communication with a second power source 244, the power inputs 209 and 212 are in power-receiving communication with a third power source 245, the power inputs 213 and 216 are in power-receiving communication with a fourth power source 246, the power inputs 217 and 220 are in power-receiving communication with a fifth power source 247, and the power input 221 is in power-receiving communication with a sixth power source 248. The power output 232 is in power-providing communication with a load 249, the power output 233 with a load 250, and so on for loads 251 through 253.
More source breakers and load breakers may be provided if there are more power sources and more loads.
In this embodiment, no power source need have the capacity to service more than one load. The first load 249 can be serviced by either the first power source 243 or the second power source 244, the second load 250 by either the second power source 244 or the third power source 245, and so on. If power ceases to be available from any power source or if any source breaker trips, the controller is in communication with the source breakers to cause the source breakers to establish electrical power connections between the remaining power sources and loads in sequence such that no load is connected to more than one source at any time.
As shown in
If a power source fails, the following sequence of operations occurs:
The resulting state of affairs is indicated in
In more traditional power systems, a given number of loads would require two power sources per load to be sure each load had a backup power supply if needed. An advantage of the circuit of
The switchboards and load breakers are arranged in groups of four. The switchboards 300, 304, 308 and 312, and the load breakers 316, 318, 320, and 322 are arranged in a group referred to as a breaker unit 324. Similarly, other groups of four switchboards and four load breakers are arranged as breaker units 325, 326, 327 and 328. These groupings are only for convenience in this discussion and do not necessarily indicate a required configuration. Separate or combined switchboards are only for convenience of installation and do not affect the operation as described above and below. The first and third switchboards 300 and 308 have a common first power input 329, and the second and fourth switchboards 304 and 312 have a common second power input 330. The first and second load breakers 316 and 318 have a common power output 331, and the third and fourth load breakers 320 and 322 have a common power output 332. Similarly the second breaker unit 325 has first and second power inputs 333 and 334 and power outputs 335 and 336, and so on for the third, fourth, and fifth breaker units 326, 327, and 328.
A first power source 349 is in power-providing communication with the power input 329. A second power source 350 is in power-providing communication with the power inputs 330 and 333, a third power source 351 with the power inputs 334 and 337, a fourth power source 352 with the power inputs 338 and 341, a fifth power source 353 with the power inputs 342 and 345, and a sixth power source 354 with the power input 346.
First through fifth loads 355 through 359 are in power-receiving communication with the power outputs 331, 335, 339, 343, and 347, respectively. Similarly, sixth through tenth loads 360 through 364 are in power-receiving communication with the power outputs 332, 336, 340, 344, and 348, respectively. More breaker units may be provided if there are more power sources and loads.
A control 365 is shown as communicating with all the breakers. A single control is shown, but the control 365 may actually comprise a plurality of controls with any suitable communication arrangement as discussed above in more detail.
No power source has the capacity to service more than two loads. The first load 335 can be serviced by either the first power source 349 or the second power source 350, as can the sixth load 360. The second load 356 can be serviced by either the second power source 350 or the third power source 351, as can the seventh load 361, and so on. If power ceases to be available from any power source or if any source breaker trips, the controller 365 is in communication with the source breakers to cause the source breakers to establish electrical power connections between the remaining power sources and loads in sequence such that no power source is connected to more than two loads at any time.
As shown in
If a power source fails, the following sequence of operations occurs:
In another example, as shown in
A load isolation breaker 424 is in power-receiving communication with the source isolation breaker 402. The load isolation breaker 424 has a shunt trip 426. The lockout relay 404 is in controlling communication with the shunt trip 426. In some examples the power and controlling communications between the main switchboard 400 and the load isolation breaker 424 are carried over conductors in a raceway 428. The load isolation breaker 424 is in power-providing communication with a power output 430.
In some examples the switchboard 400 has a second source isolation breaker 432 and lockout relay 434 in power-receiving communication with the utility and tie breakers 408 and 414. A second load isolation breaker 436 and shunt trip 438 are in communication with the second source isolation breaker 432, for example through a raceway 440. The second load isolation breaker 432 is in power-providing communication with a power output 442. Power outputs 430 and 442 are not two sources to the same load, such as from breakers 316 and 318 to load 355 in
The control 420 is in communication with the breakers to close the utility breaker 408 if power is available from a first power source 444 connected to the first power input 406, for example public utility power, to provide power to the source isolation breaker 402 and, if present, to the second source isolation breaker 432. If power is not available, or becomes unavailable from the first power source 444, the control 420 opens the utility breaker 408 and closes the auxiliary and tie breakers 412 and 414 to provide power from an auxiliary power source such as a generator 446 to the source isolation breakers 402 and 432. In some examples the control 420 causes the generator to start prior to closing auxiliary breaker 412. If power is not available from the generator 446 but is available from a load bank bus 448, the control 420 closes the tie and load-bank breakers 414 and 418 to provide power from the load bank bus 448 to the source isolation breakers 402 and 432. Only one of the source isolation breakers is closed at any one time, so no more than one load is powered from the source isolation switchboard 400. In some examples, if power is not available from either the first power source 444 or the generator 446, the control 420 may locate another generator that is not being used and may cause it to start and be switched onto the load bank bus 448 to provide power to the source isolation breakers. This is an example of Fix-One Break-OneSM logic.
As in the examples discussed above, the various components of this example need not be installed in one switchboard and may instead be mounted in other ways without affecting operation of the circuit.
The source isolation breakers 510 through 523 connect to load isolation breakers 524 through 537, respectively. The load isolation breakers have shunt trips (not shown). The first two load isolation breakers 524 and 525, which could be enclosed in a single switchboard as described above, connect to a first load 541, the next two load isolation breakers 526 and 527 connect to a second load 542, and so on through a seventh load 547. In this example the loads 541 through 544 are in the first subsystem and may be any kind of load as discussed previously. The loads 545, 546, and 547 are chiller units in this example, but in other examples other kinds of loads could be connected.
The MSB 501 receives power from a primary source 551, the second MSB from a primary source 552, and so on. As discussed previously, the primary sources may be utility power supplies or some other electrical power sources. Similarly, the MSB 501 receives auxiliary power from a source such as a generator 561, the second MSB 502 from a generator 562, and so on. In addition, each MSB is connected to a load bank bus 570. Other components, such as a data bus (not shown) may also be included in one or both subsystems. One controller such as a PLC may control all the MSBs in each subsystem, or one controller may control the MSBs in both subsystems, or each MSB may have its own controller.
As shown in
An example of a method of managing electrical power in a power distribution system having more power sources than loads, is shown in
Returning to decision block 604, if the first source breaker has been tripped, the first source breaker is locked out (612) and the first load breaker is also locked out (614), for example to isolate the first source and any wiring between the first load breaker and the first source.
Returning to decision block 606, if it is not safe to apply power from a second source, for example if another load breaker trips when an attempt is made to apply power from the second source, the load is shut down (616).
Returning to decision block 608, if the second power source is already in use, another power source not in use is identified (618). A load drawing power from a power source adjacent the one not in use is switched to the one not in use (620). If this step frees up the previously-identified second power source (622), power is provided to the load from the second source through a second source breaker and a second load breaker (610). Returning to decision block 622, if this step does not free up the previously-identified second power source, the process is repeated until the second power source is free. This is an example of the application of Zipper LogicSM functionality as already described previously.
Another example of a method of managing electrical power in a power distribution system having more than one subsystem and auxiliary power sources is shown in
In the foregoing examples, as already discussed the controls may be implemented as PLCs. Such a PLC may be switchable between an automatic mode in which the PLC controls its breakers and a manual mode in which the breakers can be electrically operated through pushbuttons subject to interlocks as already described. The breakers themselves may also have manual controls that override interlocks except a continuous signal to a shunt trip. Each PLC can monitor more than one transfer breaker pair in one switchboard, thereby providing redundancy in case a PLC fails.
A master PLC may be provided for an entire system including multiple subsystems, for example to provide a user interface that shows the status of all breakers, provides on-line diagrams, transmits user commands to other PLCs, and the like. Digital signals may be transmitted by coaxial network cables, a digital out-digital in method, or other suitable data conductors.
In systems having a load bank bus, the bus may be used for such purposes as testing generators or other auxiliary power units one at a time, startup commissioning, periodic testing, and re-commissioning after repair, as well as the load transfer functions described above.
In some examples Schneider/Square-D type NW breakers were used for source isolation and type RJ or RK breakers were used for load isolation. The PLCs were provided by Schneider/Square-D/Modicon and in some instances used Intel Pentium 651-60 central processors. Software such as Concept software and Unity software may be used. These component selections are not critical, and similar components from other suppliers could also be used.
In one example each lockout relay is controlled directly by its associated source breaker. If the breaker trips, an auxiliary contact that closes when the breaker trips is actuated connecting control power to the lockout relay. The lockout relay is a two-state relay and is electrically operated by the breaker contact to transition from reset to tripped. To transition back requires manual operation of a handle on the relay, and this cannot be done if voltage is still being applied to the relay, which is the case if the breaker is still in the tripped condition. The downstream shunt trip associated with the load breaker is activated by a contact on the lockout relay that closes when the lockout relay is activated. The load breaker cannot be reset as long as power is being applied from the lockout relay to the shunt trip.
This patent application claims priority from the applicant's Provisional Patent Application Ser. No. 61/862,446, filed Aug. 5, 2013, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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61862446 | Aug 2013 | US |