The Ramp Test (Figure 4-54) performs a steady-state pick-up or drop-out test by ramping an Action quantity from an offset value toward a limit value, similar to the Linear Ramp Macro in ProTesT® software.
Figure 4-54 Test Tab for a Single Stepped Ramp Test
The ramp test is not linked to any relay parameters or functions, except for the default frequency that can be changed; however, it does use the signal triggers defined on the Digital Inputs and Triggers subtab of the Connections &
Signals tab (see “Connections & Signals” on page 3-2). The test is configured using tools in the Test tab.
Action quantity may be one of the following:
• Voltage amplitudes
• Current amplitudes
• Voltage phase angles
• Current phase angles
• Frequency of voltage and/or current To set up a Ramp:
1. On the Test Configuration tab, select Auto Ramp or Manual Ramp.
2. Select Voltage, Current, or Frequency.
3. Select either Amplitude or Phase Angle. If you selected Frequency in step 1, these fields are disabled.
4. Select Stepped or Pulsed. If you selected Frequency in step 2, the choices are Stepped and Smooth.
The test allows for three kinds of ramp: a single ramp from an offset toward a limit (stepped); a double ramp, which ramps toward a limit, stops on relay pickup, waits a bit, and ramps back in the opposite direction to dropout (pulsed); and frequency ramp of voltage and/or current sources (smooth).
A stepped ramp is a simple linear ramp that proceeds in staircase fashion (Figure 4-55).
Figure 4-55 Stepped Ramp
A pulsed ramp returns to offset after every ramp step (Figure 4-56). Pulsed ramp is useful for testing high-set overcurrent elements to avoid thermal damage to relays. It also more closely simulates relay dynamic behavior.
This option is not available for Manual Ramp.
Figure 4-56 Pulsed Ramp
With a smooth ramp (Figure 4-57), the frequency of one or more AC sources is ramped from an offset value until the relay operates or until a limit frequency is reached (recorded as No Op).
Figure 4-57 Smooth Ramp
5. Enter the Number of Ramps and check the With Timer check box (Frequency only), if desired.
6. Click the Source Configuration button. The following dialog box appears.
Figure 4-58 Source Configuration Dialog Box
To create a current linear ramp, select an F6000 source configuration. The Sources table changes accordingly, adding or deleting rows to correspond to the number of voltages and currents, with source signals named VA, VB, VC, IA, IB, IC, and so on.
7. In the Sources table (on the Test tab), enter volts and amperes, phase angles (Ph-N), and frequency values.
The ramp quantity is identified by entering A for Action in the appropriate cell; for example, for a current ramp, IA is given Action amplitude. For phase angle ramp, relative phase angle action like A-120 or A+75 may be entered for other phases but one of them must be Action.
8. Fill in the parameters that control the Action ramp:
• Offset and offset duration (length of time to remain at the offset before the ramp begins) values can be zero or some prefault value for current;
for voltage, normal prefault voltage would normally be used, but zero may be used also; for frequency, enter normal base frequency.
• Delta value and Delta Time specify the ramp increments; each step is held for Delta Time before the next step. This allows the relay to detect the change.
• The Limit value determines when the ramp stops, if the relay has not already output a trip signal. For current, the limit value (or the offset, whichever is higher) also determines the source range required for the Action source. Normally an offset somewhat below the expected pickup and a limit not too much higher is used. If the relay does not operate, a NoOp result is recorded.
• An action multiplier is available in the Amplitude column of the source table in the Test tab. The form is A*n, where n is a constant from 0.001 to 1000, in increments of 0.001.
9. Click the Digital Output button. The following dialog box appears.
Figure 4-59 Digital Outputs Dialog Box
For information on using the Digital Outputs dialog box, refer to “Digital Output Dialog Box” on page 4-74.
Pulsed Ramp
For a Pulsed ramp there are two additional Action details: Pulse Duration and Wait (Figure 4-60).
A ramp can go either up or down. For example, a current ramp can start low (load current) and ramp to a high limit (fault current), or a voltage ramp can start high (normal voltage) and ramp down toward a lower limit (undervoltage fault). For a negative ramp direction, enter a negative Delta value.
Enter the offset and offset duration as you would for a simple ramp; this should be a normal, non-operating value. The initial current would be close to the pickup setting. The ramp proceeds from there to the limit. After each ramp step, however, the test value returns to the offset for a Wait time, which should be long enough for the relay windings to cool down and for the relay to return to a quiescent state before the next incremental pulse.
Figure 4-60 Action Details for a Pulsed Ramp
Double Ramp
Enter parameters for double ramp Action (Figure 4-61) in the same manner as for a single ramp. After the Ramp 1 Limit, enter a Wait time to allow relay output to stabilize before starting Ramp 2 in the opposite direction. The wait time begins when the trip signal occurs. Ramp amplitude can either start low, go higher, then go back down, or it can start high, go lower, then go back up.
Figure 4-61 Action Details for a Double Ramp
1. On the Test Configuration tab, select a trigger name from the drop-down menu (defined on the Connections & Signals tab; see “Connections &
Signals” on page 3-2) to identify which F6000 input is used and the transition, such as Open to Close.
2. Specify the Delay and Duration.
These values enable the trigger signal to be conditioned to ensure a solid pickup by the relay. When each ramp step occurs, the F6000 can disable the trigger input for the sense Delay time, to allow relay output to stabilize. Once the signal input is armed, if a trip signal occurs, a sense Duration timer is started; if the trip signal drops out before the timer expires, no trip is recorded. This allows debouncing of contact chatter.
These values are sometimes useful for older electromechanical relays to allow the ramp to yield a good test result. Numerical relays do not require this, so Delay and Duration can normally be set to zero.
3. Select time units in cycles, milliseconds, or seconds. Changing the time units converts all time values to the selected unit.
4. In the Measurements area at the bottom left, enter a descriptive name for Test Objective, the expected value (setpoint), and ± tolerance percentages.
The expected values are named variables, Exp1 and, in a double ramp, Exp2, which can be used in formulas in other cells of the test definition.
For example, in a double ramp, the third row of the measurement table uses a default formula of Exp1/Exp2 to compare the expected values.
(You can change this default formula.) The formula used to compare the expected values is also used to compare the actual values.