1. A liquid discharging apparatus configured to discharge liquid, comprising:
a liquid discharging head having a nozzle, and a driving element configured to cause the liquid to be discharged from the nozzle;
a driving device configured to apply a voltage to the driving element to drive the driving element;
a power unit configured to generate the voltage to be applied to the driving device to drive the driving element;
a switch configured to perform switching of voltage supply by which the voltage is supplied from the power unit to the driving device; and
a controller configured to:
control the power unit to raise a power supply voltage of the power unit up to a first voltage, under a condition that the power unit is activated;
control the switch to start the voltage supply from the power unit to the driving device while the power supply voltage is being raised up to the first voltage; and
control the driving device to apply the voltage supplied from the power unit to the driving element, under a condition that the voltage supply from the power unit to the driving device is started while the power supply voltage is being raised up to the first voltage.
2. The liquid discharging apparatus according to claim 1, wherein under a condition that the voltage supply from the power unit to the driving device is started while the power supply voltage is being raised up to the first voltage, the controller controls the driving device to continuously apply the voltage supplied from the power unit to the driving element.
3. The liquid discharging apparatus according to claim 1, wherein under a condition that the voltage supply from the power unit to the driving device is started while the power supply voltage is being raised up to the first voltage, the controller controls the driving device to convert the voltage supplied from the power unit to a pulse signal, and to apply the pulse signal to the driving element.
4. The liquid discharging apparatus according to claim 2, wherein the controller is configured to control the power unit to raise the power supply voltage up to the first voltage in a stepped manner via a plurality of voltage-raising steps for each of which a control target value is individually set;
the controller is configured to perform checking whether or not the power supply voltage reaches the control target value set for each of the voltage-raising steps, for a number of times predetermined for each of the voltage-raising steps; and
the checking of the power supply voltage is performed for a number of times in an intermediate voltage-raising step included in the plurality of voltage-raising steps and having the control target value set to be lower than the first voltage is smaller than a number of times for which the checking of the power supply voltage is performed in a final voltage-raising step, of the plurality of voltage-raising steps, having the control target value set to be the first voltage.
5. The liquid discharging apparatus according to claim 2, wherein under a condition that the power supply voltage becomes not less than a second voltage lower than the first voltage while the power supply voltage is being raised up to the first voltage, the controller controls the switch to start the voltage supply from the power unit to the driving device.
6. The liquid discharging apparatus according to claim 2, wherein the driving element is a piezoelectric element.
7. The liquid discharging apparatus according to claim 2, wherein the driving element includes a plurality of driving elements, and
wherein under a condition that the voltage supply is started from the power unit to the driving device, the controller applies the voltage only to one of the plurality of driving elements.
8. The liquid discharging apparatus according to claim 7, wherein the driving device and the plurality of driving elements are connected via a plurality of wirings, respectively;
the controller is configured to control the driving device to apply the voltage to a certain driving element, among the plurality of driving elements, connected to a wiring, of the plurality of wirings, of which resistance is greatest among the plurality of wirings.
9. The liquid discharging apparatus according to claim 3, wherein the controller is configured to control the driving device to raise a voltage level of the pulse signal as the power supply voltage is being raised to be higher; and
the controller is configured to control the driving device to increase a number of pluses per unit time of the pulse signal to be greater, as the voltage level of the pulse signal is lower.
10. The liquid discharging apparatus according to claim 3, wherein when the liquid is discharged from the nozzles in a state that the power supply voltage has reached the first voltage, the controller controls the driving device to apply a discharge pulse signal to the driving element corresponding to the nozzles, respectively; and
the controller controls the driving device to increase a number of pulses per unit time for the pulse signal applied by the driving device to the driving element, while the power supply voltage is being raised, to be greater than a number of pulses per unit time for the discharge pulse signal.
11. The liquid discharging apparatus according to claim 3, wherein under a condition that the power supply voltage becomes not less than a second voltage lower than the first voltage while the power supple voltage is being raised up to the first voltage, the controller controls the switch to start the voltage supply from the power unit to the driving device.
12. The liquid discharging apparatus according to claim 11, wherein the driving element is a piezoelectric element; and
the driving device includes a first switching element and a second switching element, the first and second switching elements being arranged between ground and a power line connecting to the power unit, the first switch being configured to apply the voltage to the piezoelectric elements to store electricity in the piezoelectric elements, and the second switch being configured to lower the voltage of the piezoelectric elements to the ground and to discharge the electricity from the piezoelectric elements,
wherein the driving device is configured to switch a ONOFF state of the first and second switching elements to apply the pulse signal to the piezoelectric element; and
under a condition that the power supply voltage becomes not less than a third voltage which is higher than the second voltage and lower than the first voltage, the controller controls the driving device to start application of the pulse signal to the piezoelectric element.
13. The liquid discharging apparatus according to claim 1, wherein the controller controls the driving device to apply the voltage supplied from the power unit to the driving element under a condition that a voltage-raising state of the power supply voltage is in a voltage-raising step included in the plurality of voltage-raising steps and performed at least one step before a final voltage-raising step, of the plurality of voltage-raising steps, in which the power supply voltage is raised to the first voltage.
14. The liquid discharging apparatus according to claim 13, wherein the driving element includes a plurality of driving elements, and
wherein the controller is configured to control the driving device to apply the voltage supplied from the power unit to all of the plurality of driving elements.
15. A liquid discharging apparatus configured to discharge liquid, comprising:
a liquid discharging head having a nozzle, and a driving element configured to let the liquid discharge from the nozzle;
a driving device configured to apply a voltage to the driving element to drive the driving element;
a power unit configured to generate the voltage to be applied to the driving device to drive the driving element;
a switch configured to perform switching of voltage supply by which the voltage is supplied from the power unit to the driving device; and
a controller configured to:
control the power unit to raise a power supply voltage of the power unit up to a first voltage in a stepped manner via a plurality of voltage-raising steps, under a condition that the power unit is activated;
control the switch to start the voltage supply from the power unit to the driving device while the power supply voltage is being raised up to the first voltage; and
control the driving device to apply the voltage supplied from the power unit to the driving element at a same time when a voltage-raising state of the power supply voltage proceeds to a final voltage-raising step, of the plurality of voltage-raising steps, in which the power supply voltage is raised to the first voltage.
16. The liquid discharging apparatus according to claim 15, wherein provided that the power supply voltage fluctuates at a period T when the voltage-raising state of the power supply voltage proceeds to the final voltage-raising step, the controller controls the switch to start the voltage supply from the power unit to the driving device after a time half the period T elapses since the voltage-raising state of the power supply voltage has proceeded to the final voltage-raising step.
17. The liquid discharging apparatus according to claim 15, wherein the driving element includes a plurality of driving elements, and
wherein the controller controls the driving device to apply the voltage supplied from the power unit to all of the plurality of driving elements.
18. A liquid discharging apparatus configured to discharge liquid, comprising:
a liquid discharging head having a nozzle, and a driving element configured to cause the liquid to be discharged from the nozzle;
a driving device configured to apply a voltage to the driving element to drive the driving element;
a power unit configured to generate the voltage to be applied to the driving device to drive the driving element;
a switch configured to perform switching of voltage supply by which the voltage is supplied from the power unit to the driving device; and
a controller configured to:
control the power unit to raise a power supply voltage of the power unit up to a first voltage in a stepped manner via a plurality of voltage-raising steps, under a condition that the power unit is activated;
control the switch to start the voltage supply from the power unit to the driving device while the power supply voltage is being raised up to the first voltage; and
control the driving device to apply the voltage supplied from the power unit to the driving element immediately after the voltage-raising state has proceeded to a final voltage-raising step, of the plurality of voltage-raising steps, in which the power supply voltage is raised to the first voltage.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for determining a location of a phase-to-earth fault on a three-phase electric line of an electric network, the method comprising:
monitoring current and voltage quantities of the three-phase electric line at a measuring point;
determining, after a fault occurs in the three-phase electric line and when the ratio of a fault current and load current has a first value, a first fault distance line which indicates an estimate of the distance of the fault from the measuring point in relation to an equivalent load distance on the basis of values of the monitored current and voltage quantities and an equation which relates the monitored current and voltage quantities to the fault distance, wherein the equivalent load distance indicates a distance of an equivalent load point from the measuring point which equivalent load point equals to a total load of the electric line modelled to be concentrated in a single point of the electric line;
determining, when the ratio of the fault current and load current has a second value which differs from the first value, at least one second fault distance line which indicates an estimate of the distance of the fault from the measuring point in relation to the equivalent load distance on the basis of values of the monitored current and voltage quantities and an equation which relates the monitored current and voltage quantities to the fault distance;
determining a distance or distances from the measuring point at which the determined fault distance lines intersect when superimposed; and
determining the distance between the measuring point and the point of fault on the basis of the determined distance or distances of intersection.
2. The method of claim 1, wherein one second fault distance line is determined.
3. The method of claim 2, wherein the distance from the measuring point at which the first fault distance line and the second fault distance line intersect is determined as the distance between the measuring point and the point of fault.
4. The method to of claim 1, wherein more than one second fault distance lines are determined such that the ratio of the fault current and load current has a different value each time.
5. The method of claim 1, wherein an average of the distances from the measuring point at which the determined fault distance lines intersect is determined as the distance between the measuring point and the point of fault.
6. The method of claim 1, comprising varying the ratio of the fault current and load current by changing the switching state of the electric network.
7. The method of claim 1, wherein the fault distance lines are represented graphically.
8. The method of claim 7, wherein the determination of the distance at which the fault distance lines intersect is performed visually.
9. The method of claim 1, wherein the fault distance lines are represented by one or more equations.
10. A computer program product comprising
computer program code, wherein the execution of the program code in a computer causes the computer to carry out the method of claim 1.
11. An apparatus for use in localization of a phase-to-earth fault on a three-phase electric line of an electric network, the apparatus being configured to
monitor current and voltage quantities of the three-phase electric line at a measuring point;
determine, after a fault occurs in the three-phase electric line and when the ratio of a fault current and load current has a first value, a first fault distance line which indicates an estimate of the distance of the fault from the measuring point in relation to an equivalent load distance on the basis of values of the monitored current and voltage quantities and an equation which relates the monitored current and voltage quantities to the fault distance, wherein the equivalent load distance indicates a distance of an equivalent load point from the measuring point which equivalent load point equals to a total load of the electric line modelled to be concentrated in a single point of the electric line; and
determine, when the ratio of the fault current and the load current has a second value which differs from the first value, at least one second fault distance line which indicates an estimate of the distance of the fault from the measuring point in relation to the equivalent load distance on the basis of values of the monitored current and voltage quantities and an equation which relates the monitored current and voltage quantities to the fault distance.
12. The apparatus of claim 11, wherein the apparatus is configured to detect a fault on the three-phase electric line and a faulted phase of the three-phase electric line.
13. The apparatus of claim 11
wherein the apparatus is configured to determine one second fault distance line.
14. The apparatus of claim 11
wherein the apparatus is configured to determine more than one second fault distance lines such that the ratio of the fault current and load current has a different value each time.
15. The apparatus of claim 11, wherein the apparatus is configured to:
determine a distance or distances from the measuring point at which the determined fault distance lines intersect when superimposed; and
determine the distance between the measuring point and the point of fault on the basis of the determined distance or distances of intersection.
16. The apparatus of claim 13, wherein the apparatus is configured to determine the distance from the measuring point at which the first fault distance line and the second fault distance line intersect as the distance between the measuring point and the point of fault.
17. The apparatus of claim 14, wherein the apparatus is configured to determine an average of the distances from the measuring point at which the determined fault distance lines intersect as the distance between the measuring point and the point of fault.
18. The apparatus of claim 11, wherein the apparatus is configured to output the determined fault distance lines.
19. The apparatus of claim 18, wherein the apparatus is configured to output the determined fault distance lines in a graphical form.
20. The apparatus of claim 18
wherein the apparatus is configured to output the determined fault distance lines mutually superimposed.
21. The apparatus of claim 11, wherein the apparatus is configured vary the ratio of the fault current and load current by changing the switching state of the electric network.
22. The apparatus of claim 11, wherein the apparatus is a protective relay.