Conservation Voltage Reduction: Smart Grid Feeder Simulator

Substation & Feeder

Substation voltage (LTC tap) 124.0 V ANSI C84.1 Range A for a 120 V service is 114–126 V. Push the tap down to cut demand — as long as the far end of the feeder stays inside the band.

Load mix — ZIP exponent k 1.0 k=0: constant-power loads (electronics, no CVR effect). k=2: constant-impedance loads (resistive heat, lighting — full quadratic drop). Real feeders mix both.

Load per house at 120 V 3.5 kW

Conductor resistance / span 0.12 Ω Longer or thinner feeders (higher Ω) drop more voltage between the substation and the last house.

Live Readouts

Substation V₀

124.0 V

Feeder-end V (min)

120.9 V

Total feeder demand

83.2 kW

Demand cut vs. 126 V baseline

2.1 %

ANSI C84.1 Range A

PASS

How it works

Conservation Voltage Reduction (CVR) is a real utility technique: deliberately running a distribution feeder near the bottom of the allowed voltage band, because many loads draw less real power at lower voltage. The relationship is the ZIP model:

P(V) = P₀ · (V / V_nom)^k
  k = 0  → constant power   (no CVR benefit)
  k = 1  → constant current
  k = 2  → constant impedance (P ∝ V², largest CVR benefit)

The feeder itself is solved with the same backward–forward sweep distribution engineers use for radial networks:

1. Guess a voltage V_i at every house (start at V₀).
2. Backward sweep: I_i = P(V_i) / V_i at each house;
   sum downstream currents into each span current.
3. Forward sweep: walk from the substation outward,
   V_i = V_(i-1) − I_span · R_span.
4. Repeat until V converges (a few iterations).

Because load current depends on voltage and voltage depends on load current, the system is nonlinear — this iterative sweep is exactly how it is solved in practice, not a closed-form formula.

Substation voltage slider — models the load-tap-changer (LTC) at the substation regulator.
ZIP exponent k — the real-world "CVR factor" depends on how much of the neighborhood's load is resistive/impedance-like versus constant-power electronics.
Feeder-end voltage is the worst case — the last house always sees the lowest voltage on a radial feeder, so it is what utilities check against the ANSI floor (114 V) before lowering the tap further.

Utilities that run CVR programs typically report 0.5–3% total energy reduction feeder-wide — small per house, large across a grid.

Over-voltage (>126 V) Within ANSI Range A Under-voltage (<114 V)

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