The most significant feature of the STVI is its ability to provide the user with a very simple way to manually test, for both commissioning and maintenance, from the simple overcurrent relay to the most complex relays manufactured today. Manual operation is simplified through the use of a built-in computer operating system and the touch screen. The STVI eliminates the need for a computer when testing virtually all types of relays. Intuitive menu screens and touch screen buttons are provided to quickly and easily select the desired test function.
Here's how easy it is
Manual Test Screen
In the following Manual Test Screen the pre-selected outputs are set using the touch screen, or power-up preset default values maybe automatically set from the user defined configuration screen. The user can select from a variety of test options including manual control using the control dial, a dynamic sequence of tests to include trip and reclose operations, an automatic ramp, pulse ramp, or pulse ramp binary search to determine pickup or drop out of relay contacts, or perform relay specific timing tests. By pressing the ON button, the selected output indicators will change colors indicating which outputs are energized.
A vector graph indicates the relative phase angles of all of the outputs. The user may select to have all output amplitudes metered to provide real time verification of all of the selected outputs, or have setting values displayed.
In the Manual test screen the user can set Prefault and Fault values. The user can toggle back and forth between the two values to monitor contact activity. To do a simple timing test the user can set Prefault time duration in seconds, and then press the Blue Play button. The Prefault values will be applied for the Prefault time, then change to the Fault values and start the Timer running. When the relay trips, it will stop the timer, and may turn selected outputs off depending on the user defined Auto-Off configuration.
Manual Multi-Phase Test Control
In the STVI Manual test screen the user can interface with multiple SMRT units to form a multi-phase test system and manually, or dynamically, control all outputs with the STVI. For example, the following is an STVI manual test screen example of two SMRT36 units interconnected using a single Ethernet cable. To the STVI user it appears as a single six-phase test system (or two three phase systems) with manual control of all outputs from the touch screen.
Auto Ramp, Pulse Ramp and Binary Search Features
The STVI may be used to determine pickup or dropout of various types of relays. Pressing the Auto Ramp button presents three choices; Step Ramp, Pulse Ramp, and Pulse Ramp Binary Search. The first selection, Step Ramp, will ramp the output by applying a value and then waiting a specific amount of time before incrementing. For example, to automatically ramp output current the user will select the channel to be ramped, input Start and Stop Amplitudes, an Increment (A), and a Delay time in Cycles (B). See the following figure.
Pulse Ramp will start at user defined prefault condition, increment up or down returning to the prefault condition between each increment. Instead of Delay time the user sets the Pulse Cycles time, which applies the fault value to the relay for the specified time. The user can select a 2nd, 3rd and 4th ramp if desired, changing the size of the increment with each ramp. This feature is most used when doing instantaneous pickup tests. The output current, or voltage, can be incremented in large steps getting to the pickup point quickly, and then reduce the size of the increment to zero-in on the pickup value. This reduces the test time, heating of the relay under test, and provides a very accurate test result. This feature is also used when testing multi zone distance relays using three phase voltage and currents. Set the Pulse Cycles duration just long enough for the intended zone to operate. If you are not sure exactly where the pickup value of the relay is, you can use the Pulse Ramp Binary Search feature.
Timing Test Feature
Pressing the Time test button on the top menu bar, the user is presented a menu of relays to test. Built-in timing tests are provided for a wide variety of protective relays, including Overcurrent, Voltage, and Frequency relays. To make it even easier and faster, the STVI has IEEE and IEC standard time curve algorithms built-in. In addition, the STVI also includes time curves and time curve algorithms for hundreds of different specific relays selectable by manufacturer, model number, and curve shape (inverse, very inverse, definite time etc.). In the following example, the G.E. IAC-51 relay with a 2 Amp Tap and a number 5 Time Dial was selected.
By entering the appropriate values in the setting screen, when the timing test is conducted, the test results will automatically be plotted and compared to the theoretical values from the relay specific time curve that was selected. If the test Multiple is changed, the appropriate theoretical trip time will change automatically.
View Test Reports
To View the test result, press the Add to Reports button. The user can now enter appropriate information relative to the test in the Test Report header. See the following example report.
Note that the software automatically compared the Operating Time to the theoretical and made a Pass Fail determination based upon the manufacturers time curve characteristic. If the recorded test point(s) is out of specification it appears red in color. If it is within specification it will be green in color. This provides excellent visual As Found reporting. Up to 8 points maybe plotted including Instantaneous trip points. If the data is imported into PowerDB reports can be generated that summarize the comments and failures of every test you perform.
State Sequence Timing Test Feature
Pressing the State Sequence button on the top menu bar takes the user to the Sequence Timing Test Screen. There are 15 programmable steps available in the Sequence Test Screen.
By default, the 9 states are already labeled as Prefault, Trip1, Reclose 1, etc. up to Lockout in step 9. Therefore, it is initially setup for a four shot trip, reclose to lockout scenario. The user is free to change the labels, or use the default labels. With each state the user may input values of voltage, current, phase angle, frequency and set the Binary Input sensing for each state. Both single pole and three pole trip can be simulated. There are default values and binary settings for a single phase trip and reclose scenario already programmed in. The user can either use the defaults or change them to suit the application. Press the Timers button to view the Timer Settings and Labels. In addition the user can view where each timer starts and stops in association with each trip and reclose operation (see the following figure).
Note that the Total Time to Lockout is also included in the setting and indicates where the total timer starts and stops. This allows for 1, 2, 3, or 4 shots to lockout including reclose times. To set the conditions for each change of state press the Wait button directly under the Timeout window. The user will be presented with several conditional settings to choose from, such as wait milliseconds, wait cycles, wait any contact (OR), and wait all contacts (AND). These are some of the conditions that the unit will take in order to determine when to change to the next state.
To set the Binary Outputs to simulate the 52a and/or 52b contacts press the smaller “more” button next to the Binary Inputs block to expand the selection window. Press on Show All Binary Outputs, and all the appropriate number of Binary Outputs, along with a select number of Binary Inputs will be displayed. In the prefault state you may choose to have Binary Output 1 contact in the closed condition to simulate breaker closed. Click on Binary Output 1 and the Binary Output setting window will appear. The default setting is Open. Click on the Close Contact Button to simulate breaker closed. Note the Name in the window is defaulted to 1. The user is free to rename it to any name or value (that will fit in the allotted space) by touching the window and use the virtual keyboard.
Once all of the Binary Inputs, Outputs, Prefault, Fault and Reclose settings are completed, the user can then press the Preview button to get a visual representation of the voltage and current outputs, as well as a visual of the binary inputs and outputs for each stage of the simulation. The following figure illustrates a sample sequence.
Press the Preview button again to return to the State Sequence test screen. To execute the test press the Blue play button. Save and review test results as previously discussed.
Adding New Features
The STVI has many powerful test features. However, there are many new features that are still to come. Megger is continuously developing new products and improving existing products. Once a new feature completes certification tests, it may be downloaded from the Megger website into the STVI as a field upgrade.
New Impedance Relay - The all new Impedance Relay Click-On-Fault
The all new Click-On-Fault (COF) is located as one of the choices under the large More >> button located next to the Help ☓ button. The new COF provides automatic tests of Impedance (distance) relays. It includes Ramp, Pulse Ramp, Pulse Ramp Binary Search, and Shot test capabilities.
Selection of Relay Operating Characteristics
Select from one the predefined generic relay characteristics of MHO, Half MHO or QUAD (Quadrilateral), or select from the relay specific Library files. The current library includes distance relays from SEL, GE, AREVA, and ABB. There are numerous other library test files which are still being tested and field evaluated. Therefore, as new relay library files become available a new version of the software will be posted to the website for download.
Definition of Operating Characteristic and Tests
There are several new innovations in the new COF that make testing distance relays easier and faster. For example, selecting the Generic MHO characteristic provides the following user input screen.
Here the user selects which Zone (up to 6 zones may be defined), type of fault, direction, tolerance values, inputs the reach, max torque (line) angle, any offset, or load encroachment settings. The software draws the operating characteristic(s) of the relay defined by the user settings. The user may select to view single zone or multiple zones. Pressing the green check button takes the user to the COF test configuration screen, as shown in the following figure.
From this screen the user can select:
Pulse Ramp Binary Search
Test Source Models
Constant Source Impedance
Creating Search Lines or Shot Test Points
The user can define up to 10 search lines or test points per fault type, per zone. Test options include;
The Independence Test option provides maximum freedom to the user to select any test line, at any angle, around the operating characteristic to define the desired test line.
The Origin Test option the user clicks a point outside the operating characteristic, and the test line will be drawn to the origin or the intercept of the R and X axis.
The Shots Test Points option is used to create one or more test points, each to replicate a fault at a particular magnitude and angle. This type of test provides a quick GO, NO/GO test of the relay after a settings change.
The user does not even have to draw the test lines. There are two Quick Test Options the user may select. The first option draws three test lines for any of the selected Quick Test solutions. The second Quick Test the user may select the desired number of test points by pressing the Test Points button and select from the list. If none of the standard phase rotations meets the user’s needs, they can enter the desired phase rotation in the window provided.
IEC 60255 Test Option
To comply with regulations which require testing to the IEC 60255 standard, the IEC 60255 option is also provided. All defined test lines will automatically be drawn perpendicular to the relay operating characteristic.
For testing relays which require a prefault load condition, the user can set the prefault load voltages and currents. This is normally used when testing accelerated tripping or dynamic over-reach characteristics.
The user then simply presses the blue Play button and the test begins. To save even more time the user can select the Play All button and the software will automatically test all define zones and faults in sequence. Based upon the user input the software will calculate all of the fault values and angles for each defined test point, and then make PASS/FAIL determination of the test results.
A real-time test screen will display the relay operating characteristic with the defined test lines in the right half of the screen with the test vector moving in the impedance plane, and in the left half it will display either the test vectors of voltage and currents being applied in real-time, or it will display the Negative, Positive and Zero Sequence vectors being applied, see the following example.
The above figure is three zone, Pulse Ramp, Phase L1-L2 fault tests being performed. Note the test amplitudes and angles are displayed in the left half, with the test results displayed in the right half.