[BUG] Wrong P_k value for the 1000 kVA LV transformer (factor of 10 too low)

[joda9]

Description

In edisgo/equipment/equipment-parameters_LV_transformers.csv the copper loss P_k
of the 1000 kVA standard transformer is clearly wrong — most likely a misplaced
decimal point. As a result the resistance of this transformer is modelled about a
factor of 10 too low in the network model.

Affected file

edisgo/equipment/equipment-parameters_LV_transformers.csv

name,S_nom,u_kr,P_k
#,MVA,%,MW
100 kVA,0.1,4,0.00175
160 kVA,0.16,4,0.00235
250 kVA,0.25,4,0.00325
400 kVA,0.4,4,0.0046
630 kVA,0.63,4,0.0065
800 kVA,0.8,6,0.0084
1000 kVA,1.0,6,0.00105   <-- 1.05 kW, should be ~10.5 kW (0.0105)

Why this is a bug

P_k (short-circuit / copper losses in MW) feeds into the per-unit resistance of the
transformer:

r_pu = P_k / S_nom — see edisgo/network/topology.py:213
(_load_equipment_data)

and from there into x_pu = sqrt((u_kr/100)^2 - r_pu^2).

Sanity check across the whole table:

Type	P_k [kW]	r_pu = P_k/S_nom
100 kVA	1.75	0.0175
160 kVA	2.35	0.0147
250 kVA	3.25	0.0130
400 kVA	4.6	0.0115
630 kVA	6.5	0.0103
800 kVA	8.4	0.0105
1000 kVA	1.05 ❌	0.00105 ❌

The P_k series increases monotonically (1.75 → 8.4 kW); the 1000 kVA value (1.05 kW)
even falls below the 100 kVA transformer and pulls r_pu down by a factor of 10.
This is not physically plausible.

Standard distribution transformers per EN 50464-1 have load losses of roughly
10.5 kW at 1000 kVA. The other rows of the table match those reference values
(e.g. 100 kVA = 1750 W, 630 kVA = 6500 W).

Expected behaviour

P_k for 1000 kVA should be 0.0105 MW (10.5 kW). This gives r_pu = 0.0105, which
lines up seamlessly with the 800 kVA value (0.0105).

Suggested fix

-1000 kVA,1.0,6,0.00105
+1000 kVA,1.0,6,0.0105

Impact

When a 1000 kVA distribution transformer is installed during grid reinforcement
(standard equipment / selection in reinforce_measures), its resistance is modelled
too low. Consequences:

• The copper losses of this transformer are underestimated in the power flow.
• The resistive voltage drop across the transformer is underestimated → potentially
  too optimistic voltage results and, in turn, possibly an understated reinforcement
  need whenever 1000 kVA transformers are involved.
• x_pu changes only marginally (≈ 0.0600 → 0.0591) and stays real — so no crash,
  just silently wrong physics.