Patent Application
20110087384
The subject matter disclosed herein relates to a system and method for operating an electrical grid, and in particular to a system and method of operating an electrical grid while conserving local or distributed capacity to provide for contingencies events.
Large complex systems often incorporate layers of redundancy. This redundancy allows the system to maintain operations even in the event of the loss or unavailability of one or more resources. For example, an electrical power transmission and distribution system 20, such as that illustrated in
Systems such as the electrical transmission and distribution system 20 often do not operate at a continuous level. Electrical demand, for example, varies over the course of the day, such as the demand curve 32 illustrated in
Since it is desirable to have high reliability during these cold and warm periods, the electrical transmission and distribution system 20 is designed to handle these short duration, but high level seasonal peaks. While a utility may have some flexibility with certain resources, such as the operation or purchase of electrical power from a power generation plant 22 for example, other resources, such as capital equipment including transformers, high voltage transmission lines and the like, need to be purchased, installed and operational well in advance of the seasonal peaks.
Having two levels of redundancy provides a high level of reliability in the delivery of electrical power to end customer even though the system includes thousands of pieces of equipment spread over hundreds or even thousands of miles. This reliability, however, does come with a price. The redundant equipment needs to be purchased, installed, and maintained to cover a small period of time during peak seasons. Thus, the electrical transmission and distribution system 20 operates with an overcapacity of resources for most of the year, and even most of the day during seasonal peaks.
Therefore, while existing electrical transmission and distribution systems are suitable for their intended purposes, there remains a need for improvements in providing high levels of reliability while decreasing overcapacity during non-peak periods.
According to one aspect of the invention, a system for operating an electrical system is provided. The system includes a plurality of sensors coupled to the electrical system. A plurality of contingency assets is coupled to said electrical system. A controller is operably coupled to the plurality of sensors and the plurality of contingency assets. The controller includes at least one processor responsive to executable computer instructions when executed on the at least one processor for activating at least one of the plurality of contingency assets to reduce electrical demand from the at least one of the plurality of contingency assets on the electrical system in response to a first signal from at least one of the plurality of sensors indicating an N−1 contingency condition has occurred.
According to another aspect of the invention, a method for operating an electrical system is provided. The method includes the steps of defining a contingency asset pool from a plurality of electrical generation and load assets. The contingency asset pool is coupled to a controller, the controller including at least one processor responsive to executable instructions comprising monitoring the electrical system with the controller. When an N−1 contingency condition is detected with the controller, at least one the plurality of electrical generation and load assets is activated from the contingency asset pool.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Traditionally electrical transmission and distribution systems 20 were are arranged to operate with what is sometimes referred to as “N−2” contingency. As used herein, the phase “N−2 contingency” means that the system may operate with the loss of two resources. These resources include, but are not limited to electrical generation facilities, high voltage transmission lines, substation equipment, circuit breakers, feeders, and transformers, for example. A typical substation may be designed to have peak capacity for operation on two transformers, use three of the transformers during normal operation and maintain a fourth transformer as a spare. In this way, if any two of the transformers were not available, such as due to preventive maintenance or equipment malfunction, the substation would still be able to operate during peak demand periods. Another example is an overloaded distribution or transmission electrical line. If an electrical line fails in one segment of the network, the remaining segments of the network would need to have sufficient capacity to carry the electrical power to the end customer.
One embodiment of an electrical transmission and distribution system 38 having sufficient capacity to manage a N−1 contingency (described in detail below) in the power generation 40, transmission 42, substation 44 and distribution 46 sections is illustrated in
The electrical transmission and distribution system 38 is arranged to deliver electrical power from the electrical power generation facilities 40 to end customers 48, 50, 52. Some of the end customers 50 have a dispatchable load 54. As will be discussed in detail below, a dispatchable load 54 is an electrical load that the customers may shutoff or disable to decrease their electrical demand on the electrical transmission and distribution system 38. Other end customers 52 have on-site electrical generation systems 56, 58 that may offset part or all of the electrical demand on the electrical transmission and distribution system 38 from the end customer 52. The on-site electrical generation systems may include diesel or natural gas fueled generators 56, or a renewable energy power source 58.
It should be appreciated that while the embodiments herein are in reference to customers 48, 50, 52 coupled to distribution segment 46, and substation 44, this is for exemplary and clarity purposes and the claimed invention should not be so limited. The electrical transmission and distribution system 38 may have a number of distribution segments 64 coupled to substation 44 and may have many additional substations and transmission segments (not shown).
The electrical transmission and distribution system 38 also includes a central control center 60. The electrical transmission and distribution system 38 operation is controlled by the control center 60. Control center 60 includes suitable electronic devices or controllers capable of accepting data and instructions, executing the instructions to process the data, and presenting the results. In one embodiment, the control center 60 includes electronic devices for monitoring and engines for simulating and presenting contingency scenarios to the operators of electrical transmission and distribution system 38. These simulation engines may be in response to data measured by sensors coupled to the electrical transmission and distribution system 38, external data such as weather reports for example, or historical information. It should be appreciated that while embodiments herein refer to a control center 60, the electrical transmission and distribution system 38 may have multiple control centers, or a hierarchy of control centers each responsible for a segment of the electrical transmission and distribution system 38 or a particular geographic area.
The control center 60 is coupled by a transmission medium 62 to equipment and sensors in the transmission 42, substation 44, distribution sections 46 and to the end customers 48, 50, 52. The transmission medium 62 may be any type of known network including, but not limited to, a wide area network (WAN), a public switched telephone network (PSTN) a local area network (LAN), a global network (e.g. Internet), a virtual private network (VPN), and an intranet. The transmission medium 62 may be implemented using a wireless network or any kind of physical network implementation or combination of implementations known in the art. Transmission medium 62 includes, but is not limited to, twisted pair wiring, coaxial cable, fiber optic cable, powerline cable, wireless, radio, infrared signal transmission systems or a hybrid or combination thereof.
During normal operation, the electrical transmission and distribution system 38 operates as illustrated in
Referring now to
In the embodiment of
It should be appreciated that while the embodiments herein describe the control center 60 detecting an event, this also includes scenarios wherein the control center 60 anticipates an issue, such as due to the result of an output from the simulation engine for example. In such an instance, the activation of the contingency asset pool 64 is a pre-emptive process by the control center 60 to mitigate or abate the anticipated problem.
The activation of the contingency asset pool 64 causes the end customers 52 to rely on their own on-site generation 56, 58 and the sectionalizing switches 66 associated with these end customers 52 open, eliminating the demand from these customers 52 on the distribution segment 46. The activation of contingency asset pool 64 may also result in the curtailing of loads, such as dispatchable load 54 for example, in end customer 50. It should be appreciated that disconnection of end customers 52 and the curtailment of loads in end customer 50 lowers the electrical demand on distribution segment 46. In one embodiment, the contingency asset pool 64 is sized to provide an N−1 contingency capacity, such that after the activation of contingency asset pool 64, the distribution segment 46 is returned to an N−1 level of contingency capacity. Thus, the electrical transmission and distribution system 38 retains an N−2 system contingency capacity even though the distribution segment 46 is arranged with equipment to provide an N−1 contingency capacity. This provides advantages in lower costs associated with purchasing, installing and maintaining additional contingency equipment in the distribution segment 46.
In another embodiment, multiple contingency asset pools 64 are provided, including contingency asset pools 64 in other portions of the electrical transmission and distribution system 38, such as distribution segment 64 for example. These additional contingency asset pools 64 may formed into either a collective pool or in a tiered arrangement to provide contingency capacity in the event an issue arises in a higher level of system, such as in transmission segment 42 or substation 44 for example. By combining the lower level contingency asset pools 64, issues arising in the power generation 40, transmission 42, or substation 44 segments may be offset providing the electrical transmission and distribution system 38 with an N−2 level of contingency capacity. Once the issue in electrical transmission and distribution system 38 has been resolved or repaired, the control center 60 deactivates contingency asset pool 64 and closes sectionalizing switches 66 and allowing electrical power to flow from the electrical transmission and distribution system 38 to the end customers in distribution segment 64.
In other embodiments, the individual assets in contingency asset pools 64, such as dispatchable load 54 or renewable energy source 58 for example, may be assigned a priority ranking. The control center 60 may use these priority rankings to create virtual contingency asset pools containing assets from different portions of the electrical transmission and distribution system 38. This provides advantages in allowing the control center 60 the flexibility to provide different responses based on the issue that arises in the electrical transmission and distribution system 38.
Referring now to
The embodiment of
It should be appreciated that the activation of contingency asset pool 72 eliminates the electrical demand 34 from the electrical transmission and distribution system 38. In the exemplary embodiment, the contingency asset pool 72 is sized to offset an N−1 contingency scenario, such as a loss of a feeder or a transformer in substation 44, the loss of electrical power generation, the loss of a high voltage transmission line, or an over-loaded transmission line for example. Once the issue in electrical transmission and distribution system 38 has been resolved or repaired, the control center 60 deactivates contingency asset pool 72 and closes sectionalizing switch 68 to allow electrical power to flow from the electrical transmission and distribution system 38 to the end customers in the contingency asset pool.
Turning now to
The relationship 81 between the asset owner and the utility may also be contractual. In one embodiment, the utility uses a reverse auctioning process where asset owners bid to participate in the contingency asset pool. The reverse auction process may be held on a periodic basis, such as daily, weekly, monthly, quarterly or annually for example. In one embodiment, the reverse auction process may be held at different defined time periods where relationships with different assets are formed for varying periods of time. In another embodiment, the contingency asset pool includes different classes of assets. Some of the classes may be available to the utility at all times, for example, while others may be available during a particular event, such as when an Independent System Operator (ISO) issues an alert or a warning for example.
With the relationships 81 for the contingency asset pool formed, the method 74 proceeds to block 82 where the electrical transmission and distribution system 38 is operated in the first or “normal” mode. When operating in this mode, the electrical transmission and distribution system 38 delivers electrical power to the end customers, and the contingency asset pool is not activated. In one embodiment, when the electrical transmission and distribution system 38 is operating in the first mode, one or more of the contingency assets may also be activated. The method 74 then proceeds to query block 84 where it is determined if there is an operational issue, such as an overloaded or malfunctioning power line, transformer or feeder for example. If the query block returns a negative, meaning there are no issues, the method 74 loops back to block 82.
If the query block 84 returns a positive, meaning that an issue has been detected or is anticipated, the method 74 proceeds to block 86 where sufficient assets to form and N−1 level of contingency capacity are activated. In one embodiment, the entire contingency asset pool is activated. In other embodiments, where the control center 60 has flexibility in the selection of assets, the control center 60 may form a virtual pool of contingency assets that are selected from a larger group. In one embodiment the virtual pool of contingency assets is selected based on the particular operation issue that is being addressed, with the selected assets forming sufficient capacity to create an N−1 contingency capacity based on the particular event. In another embodiment, the virtual pool of contingency assets are selected based on a priority ranking.
With the contingency asset pool activated, the utility provides the agreed upon incentive 89 to the participating asset operators in block 88. As discussed above, these incentives 89 may include direct financial payments, tax relief, rebates, reduced electrical tariff rates, issuance of carbon credits or nitrous oxide offsets for example. The method 74 then proceeds to query block 90 where it is determined if the operational issue continues to exist. If query block 90 returns a positive, the method 74 loops back to block 86. If query block 90 returns a negative, meaning that the operational issue has been abated, the method 74 proceeds to block 92 where the contingency asset pool is deactivated. The method 74 then loops back to block 82 where the electrical transmission and distribution system 38 is operated in the first mode.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
