Patent Application
20220328216
This invention relates generally to a surge protection apparatus and method, and more particularly to a terminal mounted electromagnetic pulse (EMP) transient voltage surge protection apparatus and method for substation protective relays.
A high-altitude detonation of a nuclear weapon can generate a large electromagnetic pulse (EMP), referred to as a high-altitude EMP (HEMP). HEMP is composed of three hazard fields that are denoted E1, E2, and E3. For purposes of clarity, the current discussion will be limited to E1 HEMP. The E1 component of HEMP is a rapid pulse of radio frequency electromagnetic energy that impacts any position on earth within line of sight of the high-altitude nuclear burst. The resulting electromagnetic plane wave that propagates to the earth's surface is generated by the interaction of the atmospheric gamma ray—generated Compton currents with the earth's magnetic field. This plane wave propagates to the earth's surface and couples to conductive lines, for example unshielded control/signal cables within an electric substation, and induces voltage and current transients (surges) that can damage connected electronic equipment such as digital protective relays (DPRs). An example of plane wave coupling to an arbitrary above ground cable that is terminated at each end by a lumped impedance is illustrated in
Presently available surge protection uses Metal Oxide Varistors (MOVs). These MOV devices are commercially available and have been used to protect equipment against lightning surges; however, MOV devices have not been used widely to protect electronic devices, such as protection and control equipment (e.g., DPRs) located in substations, from E1 HEMP surges. One MOV solution would be to use the MOV to shunt the voltage surge to ground before it propagates on to a connected device that is susceptible to voltage and current transients,
However, there are many practical issues with using MOVs in substation applications. Some of these include: (1) connecting to the equipment in the appropriate location (this can be especially difficult in substation retrofit application), (2) providing a means of determining whether the MOVs have failed or the unit is operational, (3) grouping the MOVs in a modular sense for digital protective relay applications, and (4) ensuring that the MOVs and design are sufficient to provide protection against the very fast front transients that are associated with E1 HEMP.
Retrofitting an existing substation with presently available surge protection, if it existed for EMP surges, would be expensive and time consuming (i.e., requiring extended outages). In general, cables come from devices outside the substation control building and “land” on terminal blocks at the rear of cabinets,
Thus, a surge protection apparatus and method that provides the appropriate level of surge protection while addressing the issues described above is needed.
This need is addressed by providing a surge protection apparatus that can be used for E1 HEMP and retrofitted easily to terminal blocks presently used in substation control wiring applications.
According to an aspect of the technology described herein, a surge protection apparatus includes a housing; electronics contained in the housing; and a plurality of metal tabs electrically connected to the electronics, the metal tabs being configured to connect to a terminal block of a relay panel in a substation, the metal tabs electrically connecting the terminal block to the electronics to provide EMP surge protection to the relay panel
According to another aspect of the technology described herein, a terminal mounted electromagnetic pulse (EMP) transient voltage surge protection apparatus includes a housing; electronics contained in the housing; and a plurality of metal tabs electrically connected to the electronics, the metal tabs being configured to connect to a terminal block of a relay panel in a substation, the metal tabs electrically connecting the terminal block to the electronics in parallel to provide EMP surge protection to the relay panel.
According to another aspect of the technology described herein, a method of protecting relay panels in a substation from electromagnetic pulse (EMP) transient voltages includes the steps of: providing a surge protection apparatus having: a housing; electronics contained in the housing; and a plurality of metal tabs electrically connected to the electronics, the metal tabs being configured to connect to a terminal block of a relay panel in a substation, the metal tabs electrically connecting the terminal block to the electronics to provide EMP surge protection to the relay panel; and electrically connecting the surge protection apparatus to the terminal block of the relay panel in the substation
The invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures, in which:
Surge protection of devices (not substation electronics) exposed to E1 HEMP surges has in the past been mitigated with the use of powerline filters. These powerline filters are connected in series between the cable and the device and are designed to block the transient signal. Such powerline filters are used to protect equipment connected to AC power circuits inside shielded enclosures (e.g., a desktop computer) and were never designed to protect low-voltage signal wires that are connected to digital protective relays. Because of the nature of power system protection and control circuits, series connected devices are not preferred.
Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,
As shown in
The MOVs 26 are used to shunt the incident voltage surge to ground. The fuses 25 are used to isolate the MOVs 26 from the connected circuit should they fail. Generally, the MOVs 26 fail shorted and so an MOV failure will create a short circuit to ground and could affect the operation of the protection and control system that it is connected to if the failed MOV is not automatically disconnected from the system. The LED circuit 27 is used to provide indication that the device is on-line and that the fuses 25 are not blown. When the LEDs 30 and 31 are lit, the system is operational, and when they are not, it indicates a problem has occurred.
The design of the E-SPD 10 allows the E-SPD 10 to be installed onto terminal blocks already used for substation control wiring applications,
As shown, the tabs 16 are angled to allow the E-SPD 10 to be easily installed onto existing terminal blocks 18. For example, each of the tabs 16 include two bends 40 and 42 which divide each of the tabs 16 into three sections 44, 46, and 48. The bend 40 has an angle (section 44 relative to section 46) of approximately 43 degrees to about 47 degrees and more preferably of about 45 degrees. Bend 42 has an angle (section 46 relative to section 48) of approximately 45 degrees to about 47 degrees and more preferably of about 45 degrees. It should be appreciated that a single bend or other suitable number of bends may be used. Section 44 may have a length of about 0.6 cm to about 0.67 cm and more preferably about 0.635 cm; section 46 may have a length of about 0.98 cm to about 1.06 cm and more preferably about 1.02 cm; and section 48 may have a length of about 2.04 cm to about 2.12 cm and more preferably about 2.08 cm.
As illustrated in
The current invention is advantageous because it can be connected directly to a terminal block of existing relay panels in a substation. This is in stark contrast to other devices that are DIN rail mounted or rack mounted which are not capable of being directly connected to the terminal block. Additionally, protection from fast front surges such as those generated by E1 HEMP is limited by longer ground leads, such 100's of centimeters. Mounting the surge protection devices directly to the terminal block minimizes ground lead length, for example 10's of centimeters, and improves protection.
The foregoing has described a surge protection apparatus and method. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.
Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.
The invention is not restricted to the details of the foregoing embodiment(s). The invention extends any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
