In protective relaying terminology, however, an impedance relay has a characteristic that is different from that of a relay responding to any component of impedance and therefore, the. The operating characteristic of impedance relay is shown below. For internal faults this limitation does not exist and voltages of twice the setting are easily reached resulting in fast operation of the differential relay. This relay operates only when the impedance between the source and the relay is less than that provided in the section. A number of application aspects have been discussed including shaping of the impedance characteristic, the impact of fault resistance, different. Distance relay basics free download as powerpoint presentation. More specifically, the relay operates depending upon the impedance between the point of fault. The basic principle of distance protection involves the division of the voltage at the relaying point by the measured current. Principles and protection applications of lowimpedance. Highimpedance differential relay protection use highimpedance differential elements for fast tripping for inzone faults, while providing security during heavy through faults and ct saturation. If the impedance is within the reach setting of the relay, it will operate. A typical smith chart is normalized to the system impedance. Use event reports and the sequential events recorder ser for quick postevent analysis.
Remember high impedance digital voltmeters draw almost no current. A single lowimpedance bus differential relay can provide protection for a single phase, two phases, or all three phases, depending on the number of relay current inputs. Fault current flowing through saturated ct and associated wiring generates a voltage across the relayrscombination. Since the branch current formed by these two components is low, the highimpedance bus differential relay trip becomes dependent on voltage in its terminals. High impedance busbar differential protection valence. Since the branch current formed by these two components is low, the high impedance bus differential relay trip becomes dependent on voltage in its terminals. It is available in eight versions, five of these versions each with reconnecting operate values u s1 and u s2, and three versions with continuously settable operate value between 100 and 400 v. The operating characteristic of the impedance relay, neglecting the controlspring effect, is shown in. The methods discussed most in this paper include high impedance unre.
Apr 14, 2016 the operating characteristic of impedance relay is shown below. The generator capability must be plotted on the relay operating impedance plot to determine what the loadability is in relationship to the relay settings. The differential current will stable for outside of the relay. Distance protection impedance relay is a widely used protective scheme for the protection of high or an extra high voltage transmission lines. More complex methods of controlling impedance in multistage amplifiers, using negative feedback, is dicussed in amplifiers module 3. Highimpedance bus differential protection modeling in atp. Connection and setting guide rxzk 22h underimpedance relay with directional function. Relay fuse block covers usually label the location and position of each fuse, relay, or fuse.
Reverse power relay and protection assemblies rxppk 2h, rappk. The effect of load flow is to cause a shift in this voltage relative to the relay current because the relay current ir and the total fault cur rent if are out of phase with each other. Impedance relay and protection assemblies rxzk 21h, 22h, 23h and razk 1mrk 509 006ben page 3 technical data table 1. Pdf the implementation of distance protection relay in. Principles of differential relaying current balance high impedance determine worst case throughfault current. The operating characteristic of a reactance relay is shown in the figure below. Low impedance bus differential scheme showing an external fault, f1, and an internal fault, f2. Impedance relay and protection rxzk 21h, 22h, assemblies 23h. These relays are known as distance relay or impedance relay. We will explain factors impacting performance of distance relays focusing on source. Lowimpedance bus differential scheme showing an external fault, f1, and an.
It has low operating time and starts operating instantly when the value of current is more than the relay setting. It is noteworthy here that in electrical engineering, the term impedance can be applied to resistance alone or reactance alone, or a combination of the two. A transformer is an electrical apparatus designed to convert alternating current from one voltage to another. The apparent impedance so calculated is compared with the reach point impedance. A relay that operates on the quantities given in figure 1, can be easily analyzed for the conditions of. It is clear from the characteristics that if the impedance seen by the relay lies within the circle then the relay shall operate else it wont operate. This relay operates only when the impedance between the source and the relay is. Distance relay fundamentals 63 fault, operation does not occur because izv and v are 180 out of phase. The term complex impedance may be used interchangeably quantitatively, the impedance of a twoterminal circuit element is the ratio of the complex representation of a sinusoidal voltage between its terminals to the complex representation of the current flowing through it. In other words, when the relay control coil is not energized, the relay.
In the high impedance differential relay the simple current or voltage based operated relay can be use as high impedance with the series of stabilizing resistor and withe parallel connection of metrosil in this the setting of stabilizing resistor is based on the required operating voltage in the relay and metrosil is provided for to avoid the relay to operate from through. Numerical high impedance relay with ct supervision dad n numerical high impedance relay with ct supervision description the overall differential protection uses the high impedance circulating current principle. What is the main difference between high impedance. Fault current flowing through saturated ct and associated wiring generates a voltage across the relay rscombination. A simple mho distance function, with a reach of z ohms, is shown in figure 1. Tutorial on distance and over current protection erpc. Implementing nerc guidelines for coordinating generator. Sel587z highimpedance differential relay schweitzer. Impedance relay and protection assemblies rxzk 21h, 22h, 23h and razk 1mrk 509 006ben page 5 rxzk 22h rated voltage ur 100 v rated current ir 1 a or 5 a scale constant is 0,1 0,2 0,4 and 1,0 x i r. The equation at the balance point in a simple impedance relay is k1v2 k2i2 or vi k3 where k1, k2 and k3 are constants. High impedance differential relays are some of the easiest relays to test.
The high impedance ref relay is defined as a relay circuit whose voltage. The operation of a normally closed relay is the same to that of a normally open relay, except backwards. In other words, the relay is on the verge of operation at a constant. The value of input and output impedance can be arranged to an appropriate value by the choice of amplifier design. The p72x relay together with the p79x unit, is designed for applications where. The sel587z high impedance differential relay is an economical and flexible relay that combines timeproven, high impedance analog technology with the advantages of microprocessor technology.
In other words an impedance relay is a voltage restrained over current relay. High impedance busbar differential protection will not work properly if the cts are not sized correctly for the connected circuit. The population deviation from the final solution pdfs has been. High impedance differential relay protection use high impedance differential elements for fast tripping for inzone faults, while providing security during heavy through faults and ct saturation.
Several methods of bus protective relaying are described and compared in the paper, with mainstream emphasis. They immediately release a trip signal when the impedance value is inside the zone 1 impedance circle of distance relay 1. Pdf selective, highspeed clearance of faults on high voltage transmission lines is critical to the security of the power system. Abb library is a web tool for searching for documents related to abb products and services. We calculated that the voltage across the nonsaturated ct, when another ct saturates, is 83.
A perfect match is located at the center of the chart and, thus, its normalized value is 1. Impedance relay and protection rxzk 21h, 22h, assemblies. This diagram is exact ly equal to an rx diagram except that all of the impedance. Sep 01, 2018 there is one type of relay which functions depending upon the distance of fault in the line. High impedance differential relay radha 1mrk 509 015ben page 2 design the radha relay is part of the combiflex family. For the impedance z as shown in figure, the current is lagging behind the voltage by angle o. Principles and protection applications of low impedance bus differential relay highspeed selective bus protection can do much towards limiting the effects of a busbar fault on the system. We presented full variant of this ebook in epub, doc, pdf, txt, djvu forms. If searched for a ebook impedance relay manual in pdf format, then you have come on to loyal site. Phaseplane diagram illustrating the concept of rdot principle. Practical considerations for high impedance restricted. Considerations for using highimpedance or lowimpedance. Pdf high impedance restricted earth fault protection. You should read that post first before we dig deep into the calculations and considerations that explain how high impedance busbar differential schemes function.
In other words, the relay is on the verge of operation at a constant value of vi ratio, which may be expressed as an impedance. This is true for the threephase fault shown also for a phasetophase fault and for a phase distance function only. I want to know how a high impedance differential scheme. The protection consists of instantaneousdefinite time overcurrent elements 8750 and. A single low impedance bus differential relay can provide protection for a single phase, two phases, or all three phases, depending on the number of relay current inputs. Considerations for using high impedance or low impedance microprocessor relays for bus differential protection the transformer can be seen in 10.
Distance relays fundamentals ge grid solutions online store. Calculation of distance protection settings in mutually. There are many types of distance relay characteristic. The differential current will stable for internal of the relay function.
An innovative microprocessor based busbar differential relay that offers fast and sensitive operation under internal fault conditions and ensures improved. Electrical impedance is the measure of the opposition that a circuit presents to a current when a voltage is applied. More specifically, the relay operates depending upon the impedance between the point of fault and the point where relay is installed. The relay is low impedance with a biased differential characteristic. Reduce panel design cost and space requirements by using a single relay that includes threephase protection, resistors, and metal oxide varistors movs. All smith charts in this paper are normalized to 50 ohms impedance. We covered the basic operating principles of high impedance busbar differential protection in our previous post, i want to know how a high impedance differential scheme works. There is one type of relay which functions depending upon the distance of fault in the line. A much more useful way of showing the operating characteristic of distance relays is by means of the socalled oimpedance diagramo or orxdiagram. Distance relay or impedance relay working principle types. Principles and characteristics of distance protection these relays may sometimes be set based in percentages of the line impedances, for example a typical setting for zone 1 is 80% of the impedance of the line in order to not reach the remote end, the zone 2 can be set at 120% of the impedance of the line in order to dependably overreach the.
We are providing stabilizing resistor to make the high impedance path for the relay. Practical considerations for high impedance restricted earth fault relay settings, journal of the institution of engineers india. A range of metrosil varistors, primarily based on 150mm diameter discs, has been developed to limit this voltage to a safe level. An impedance relay measures the impedance of the line at the relay location. The term complex impedance may be used interchangeably.
The left edge of the smith charts used here is zero 0 impedance and the right edge is infinite impedance. Negative sequence overcurrent relay and protection assemblies rxiik 4, raiik 400. Istance relays perationdepend on the agnitude of the current or ltage of the circuit. The impedance relay is better suited for phasefault relaying for lines of. Principles and characteristics of distance protection. Rated values rxzk 21h rated voltage ur 100 v rated current ir 1 a or 5 a scale constant is 0,1 0,2 0,4 and 1,0 x i r setting ranges. Observe that for the balance point fault, the v is exactly equal to iz. Pdf fundamentals of distance protection researchgate. Principles of differential relaying my protection guide. O reference 1 provides a comprehensive treatment of this method of showing relay characteristics. As discussed previously, the 21 relay operates by measuring impedance.
The shift in phase in the voltage is more pronounced as the impedance, zt, gets larger relative to the impedance, zs. Quantitatively, the impedance of a twoterminal circuit element is the ratio of the complex representation of a sinusoidal voltage between its terminals to the complex. Principles and protection applications of lowimpedance bus. When a fault occurs in the protected line section the measured impedance is the impedance of the line section between the relay location and the point of fault. Follow this link to ask your own question and it might appear in a future blog post high impedance differential scheme testing. X is the reactance of the protected line between the relay location and the fault point, and r is the resistance component of the impedance. An innovative microprocessor based busbar differential relay that offers fast and sensitive operation under internal fault conditions and ensures improved stability during external faults is presented. The 87z element is a sensitive, lowimpedance, adjustable pickup current element scaled in voltage 6. The time interval between the instant pickup value and the closing contacts of the relay is very low. The sel587z highimpedance differential relay is an economical and flexible relay that combines timeproven, highimpedance analog technology with the advantages of microprocessor technology. Impedance relay is protection relay which functions depending upon the distance of fault in the line. Highimpedance bus differential protection modeling in atpmodels.
Figure 2 network equivalent diagram for singlelinetoground faults. In some applications of high impedance relays for protection and control duties, the maximum internal fault current can develop high voltages that can damage the relay insulation. The operation of the conventional over current relays either direction or non directional. Relay must be able to operate even when the fault current is lower than the rated current and likewise in the even of close up faults when the output voltage from the generator disappears if the voltage drops to zero volts the relay operates for a current as low as 20% of the rated current the relay is normally set to operate at 70% of the. A transformer has no moving parts and is a completely. The 87z element is a sensitive, low impedance, adjustable pickup current element scaled in voltage 6. Considerations for using highimpedance or low impedance microprocessor relays for bus differential protection the transformer can be seen in 10.
397 850 947 1306 1251 484 1317 1258 935 939 267 975 1338 692 342 1232 290 1126 197 366 352 26 1163 1473 201 1232 341 1386 1475 610 390 1080 575 420 184 625 410 1471 900 1225 627 73 1317 1358