hties, the present Type 59 synchronous machine model program was implemented
and put into practical use in EMTP. In the first half of nineties, also Type 58 model, which has
significant improvement from the former, was put into practical use in ATP-EMTP. Most sources of AC
power systems are synchronous generators, so the dynamics of the machines are of great interest,
especially regarding relatively short time interval of phenomena. Only time domain analysis is
applicable to such fast phenomena as down to sub millisecond. In such circumstances EMTP is a
significantly useful tool in power system dynamics analyses. As the special feature of Type 58,
calculations are stable especially in asymmetrical circuit conditions such as non-transposed over-head
lines, which are mostly applied in todays power systems.
It should be noted the present type 59 involves a great bug calculation of saturation in magnetising.
The usage is mostly common by both, excepting write 58 or 59. In this chapter, therefore, mostly
Type 58 is explained.


6.1 Machine parameter coding
What are written in the Role Book, in Chapter Dynamic Synchronous Machine, are not perfectly
updated, so the present updated coding is to be shown in this section.

The figured modelling in ATP-EMTP synchronous
machine is shown in Fig. 6.1 (2P machine). Two coils
in each d and q axis model the rotor. As for the stator,
in Type 59, three phase coils are replaced by two
coils in d and q axes, whereas, in Type 58, three
phase coils are applied as they are. The basic equa-
tions in Type 58 are as follows.
For each coil voltage,



j,k : a, b, c, F, G, KD, KQ
L
jk
: time varying functions, depending on
the angle between Rotor and Stator
As for torque,


These differential equations are numerically calcu-
lated.

By inputting machine data shown later, the necessary
constants in the equations are calculated, where
some assumptions are introduced. Today, the calculations are considered appropriate in obtaining the
machine constants.
Typical data coding of Type 58 is shown below. (Others are as written in Role Book, .)





Fig. 6.1 SM modelling in ATP-EMTP
DW and QW are used only in Type 59

2

Note:

- In the 2nd and 3rd lines, only 58 and node names are to be written. Voltages, frequencies and an-
gles are automatically introduced as symmetrical three phase AC.
- < 2.0 of PARAMETER FITTING corresponds to open circuit time constants are to be used.
> 2.1 of PARAMETER FITTING corresponds to short circuit time constants are to be used.
- 1 in col. 7 of 5th line corresponds to metric unit mechanical constants are to be used.
- For R and X, p.u. values (machine rating bases) are to be applied.
- For time constants, second is to be used as the unit.
- If XCAN (Caney reactance) can be applied, transient rotor coil currents such as during short-circuiting
are more correctly calculated. For armature currents, little influence is introduced. Without introduc-
ing the value, XL value is automatically introduced as XCAN.
- To write 11, 21, 31, and 51 in Output ordering cards yields full out put for one mass machine case and
generally recommended.
- For initialising Type 58 machine, CAO LOAD FLOW option is applicable, which may introduce better
results especially asymmetrical circuit cases. The usage of which is identical to FIX SOURCE, see
data files in the following example case.


6.2 Some examples
No-load overhead line charging current supplying
In the first example, no-load overhead line charging current case is taken up. The total system layout is
shown in Fig. 6.2 where No. 2 plant and infinitive capacity of source (voltage source) are disconnected.
Only No. 1 plant generator is supplying overhead lines capacitive charging current.
The overhead line is modelled in non-transposed double-circuited type, where parameters are calcu-
lated in 50 Hz. It should be noted that in calculating machine dynamics, phenomena are mostly in
power frequency, so power frequency based line parameters are to be applied. Phase line locations
3
are a, b and c from the top in one side, and c, b and a in the other side for obtaining as better
symmetry. Details are shown in Chapter 03 of this text. As for step-up transformers, details are shown
in Chapter 04. For initialisation, by specifying the generator terminal voltages together with phase an-
gles, all variables are to be automatically fixed in this SM program. Then in the case, this procedure
was applied. For details of the data coding, see attached data file DATA6-02.DAT.
Note:

-
Transformer saturation characteristics may introduce violence in calculation. The main cause
seems to be inrush current in the magnetising circuit. SM initialisation and overriding initial condi-
tion to non-linear element (Type 93 reactor) is not compatible. In SM transient calculation, as less
influence by the saturation is supposed, such non-linear element(s) should be excluded. For in-
troducing transformer magnetising circuit, see Data6-0x.dat, where inrush current still exists.

-
Max allowable step time was approx. 100 s in the case. By longer step time, diverge may arise.
The critical value depends on also the circuit parameters (transmission line, load circuit, etc.).
Fig. 6.2 Two machines and infinitive bus system layout


a) Generator terminal voltages and currents
b) Line voltages and charging currents


c) Rotor winding currents


d) Air gap torque

Fig. 6.3 No-load transmission line charging by a synchronous generator

4
-
Generally, imaging actual systems, numerous times of Try and error process is inevitable for op-
timum calculation even such simple cases.


Some results are shown in Fig. 6.3. The HV line charging voltages and currents are shown in b) and
the generator terminal voltages and outgoing currents are in a). In HV side, asymmetry is not significant
due to the phase line location crossing. In generator side, on the other hand, some asymmetry exists in
the currents. The cause seems to be Delta-Wye connection of the step up transformer, i.e., the cur-
rents out of Delta connected coils are the subtraction of the coil currents corresponding to the HV side
currents. Subtraction often introduces higher asymmetry. The steady state rotor winding currents in
symmetrical condition are to be constant, i.e. the rotor and the armature flux rotate in an equal speed.
Nevertheless, Fig. 6.3 c) shows some fluctuations in the rated frequency. The cause seems the
asymmetry of the load (transmission line) circuit. In the torque (Fig. 6.3 d)), also ripple of doubled fre-
quency exists.


Load flow calculation
In a circuit composed of generators and voltage sources, where all voltage values and phase angles at
generator and source terminals have been beforehand correctly obtained together with appropriate
load circuit parameters, all variables within all generators are automatically initialised by giving all of
such conditions to EMTP calculation data. The previous case is a simple example.
Obtaining such voltage conditions is generally complicated and of tremendously hard work. FIX
SOURCE has been widely used for such purpose in ATP-EMTP. CAO LOAD FLOW, which was
developed lately by Mr. CAO and seems to be superior especially in cases with existing some asym-
metry in the circuit, is the same usage and is applicable only to Type 58 SM. Therefore in this section,
only CAO LOAD FLOW is explained. (Usage is mostly common to FIX SOURCE.)
In Fig. 6.2, assuming plant No. 1 (4P machine) to supply full power towards right side infinitive bus and
plant No. 2 disconnected, the data file coding is shown in Data6-03.dat attached. In the file the decla-
ration, CAO LOAD FLOW is typed before the time card. At the bottom part, the initial load flow condi-
tion is typed. In the case, generator terminal voltage and output active power are input, with typing 1
at Column 2. By this procedure, the initial terminal voltages phase angle and all machine variables
including the reactive power are automatically and appropriately calculated.
By typing 0 instead of 1, active power and reactive power (generator direction) are to be specified.
By 2, reactive power and phase angle are to be specified. By such procedure, the rest variables are
automatically and appropriately initialised.

Some results are shown in Fig. 6.4. In a), generator terminal voltage and supplying current are shown.
The current value corresponds to 1300MVA X 0.9 of full active power at 19kV. The current is slightly
lagging. On the other hand, in Fig. 6.4 b) the transmission line voltage and current are in a same phase
angle, i.e. power factor is ca. 1.0. Due to the transformers short-circuit reactance, generator side cur-
rent has some lagging component. The transmission line current value seems to just appropriate. From
the generator terminal voltage and current, the generator supplying apparent power is calculated as
1210 MVA, where the active power is specified (in CAO LOAD FLOW) as 1170 MW (= 0.9 X 1300
MVA) in the data.
c) shows detailed voltage phase angle difference along the transmission line. By existence of active
power flow, along the line towards downstream, voltage phase angle is delayed.
d) shows air gap torque and angle of the d-axis based on the infinitive bus voltage. Both are compared
to the case of no-load transmission line charging current supplying case. Values seem to be appropri-
ate, but the cause of the fluctuation in the torque is not clarified yet.